16th International Conference on Muon Spin Rotation, Relaxation and Resonance (μSR2025)

20 Jul 2025, 09:00 → 25 Jul 2025, 23:20 America/Vancouver

The 16^th International Conference on Muon Spin Rotation, Relaxation and Resonance (μSR2025) will be held in St. John’s, Newfoundland, Canada on July 20-25^th, 2025. The μSR conference is an international event held every three years. The last conference was held in Parma, Italy in 2022. 

The conference is being jointly organized by the Centre for Molecular and Materials Science at TRIUMF, Simon Fraser University, the University of British Columbia, and Memorial University of Newfoundland. It will cover all aspects of the use of muon spectroscopy and β-NMR in condensed matter, materials and molecular sciences, such as 

• Magnetism
• Superconductivity
• Hydrogen isotopes in matter
• Spintronics
• Energy storage materials
• Polymers and biomaterials
• Thin films, surfaces and interfaces
• Chemistry
• Beamlines and instrumentation   
   

while also considering applications of muons in other areas, such as elemental analysis, nuclear physics, cultural heritage, and the study of single event failures arising from the irradiation of microelectronics.

The conference will consist of invited and contributed talks as well as poster sessions. The proceedings of the µSR2025 conference will be published. Details to be determined.  

The conference will be held at the Delta Hotels St. John's Conference Centre, 120 New Gower Street, St. John's, NL, A1C 6K4. St. John's is the oldest and most easterly city in North America, and Newfoundland and Labrador's capital. Although in Canada, it’s closer to ISIS (3,660 km) and PSI (4,480 km) than it is to TRIUMF (5,022 km)!

Please contact local organizers at musr2025@triumf.ca if you have any questions.

Thank you to our sponsors

Thank you St. John's, NL

 

 

 

 

WE LOOK FORWARD TO SEEING YOU THERE!

Sunday, 20 July ¶

Student Day: Memorial University¶

Philip_Jones_Student_Day_talk.pdf

Student Day Timetable

1 Introduction to muSR¶

Speaker: Graeme Luke (McMaster University)

Intro_to_musr.pdf

2 Muon Spin Relaxations¶

Speaker: Roberto De Renzi (Department of Physics and Earth Sciences, University of Parma, IT-43124 Parma, Italy)

RobertoDeRenzi_output.mp4

3 DFT+μ : Density functional theory for muon site calculations¶

Speaker: Ifeanyi John Onuorah (University of Parma, Italy)

IfeanyiJohnOnuorah_dft+mu.pdf

4 Demonstrations of computational techniques¶

Speakers: Ifeanyi John Onuorah (University of Parma, Italy), Pietro Bonfà (Dipartimento di Scienze Fisiche, Informatiche e Matematiche, University of Modena and Reggio Emilia, IT-41125 Modena, Italy)

CoF2

F-Mu-F

IfeanyiJohnOnuorah_demo_dft+mu.pdf

muesr

5 Low Energy μSR Investigation of Helimagnetism in MnGe Films¶

Speaker: Jincheng Huang (Memorial University of Newfoundland)

presentation_studentday_jincheng.pptx

6 Muon Cascade Calculations¶

Speaker: Philip Jones (philip.d.jones@warwick.ac.uk)

Philip_Jones_Student_Day_talk.pdf

7 Development of Muon Spin Imaging¶

Speaker: Soshi Ishitani (Osaka University)

presentation_studentday_soshi.pdf

8 Atypical Vortex Lattice and the Magnetic Penetration Depth in Superconducting Sr2RuO4 Deduced by mSR¶

Speaker: Mikhail Yakovlev

MYakovlev_muSR2025_StudentDay_Sr2RuO4.pptx

9 Anomalous Magnetism in NiI2: How Structure Affects Dynamics¶

Speaker: Theo Breeze (Durham University)

NiI2_presentation_Theo_Breeze.pptx

10 Muonium Formation and Dynamics in Double Perovskites Cs2AgBiX6 (X = Cl, Br)¶

Speaker: Katie Curvelo

KCurvelo Student Day Presentation.pdf

11 μSR Data Analysis with Bayesian Neural Networks¶

Speaker: Miyahara Hiroaki (Muroran Institute of Technology)

2025_07_17_Hiroaki_Miyahara_μSR2025oral.pptx

12 β-SRF — A Facility for Depth-Resolved Characterization of the Magnetic Field Screening in Superconducting RF Materials¶

Speaker: Edward Thoeng (TRIUMF)

ET_StudentDay_new.pdf

13 Investigating Structural Relaxations in DGEBA - A Unification of Microscopic and Macroscopic Methods¶

Speaker: Benjamin Orton (STFC)

Orton_Muons conference 2025_v6_1.pptx

14 Magnetism of N(1/3)S2 (N=Fe, V): Insight into the Intercalated Transition-Metal Dichalcogenides Using muSR¶

Speaker: Nathan Bentley (University of Durham)

muSR2025studentday_NPB.pdf

Monday, 21 July ¶

Conference Event: Opening¶

Thanks.pdf

15 muSR2025 Opening¶

Speaker: Jeff Sonier (Simon Fraser University)

Opening muSR2025 21July2025.pptx

Oral Contributions¶

Convener: Graeme Luke (McMaster University)

16 Hyperfine-Enhancement as a Route to Persistent Spin Dynamics in Singlet-State Systems¶

Many magnetically frustrated systems exhibit what is known as persistent spin dynamics (PSD) in $\mu$SR experiments, the origin of which has remained mysterious since their discovery in the 1990s. As the temperature is lowered, the muon-spin relaxation rate rises (as would be expected for the slowing-down of spin fluctuations) but this rate then saturates at low temperature, the low-temperature fluctuations being interpreted as PSD. To explain this phenomenon, we describe how muons can couple to singlet states and illustrate this with experimental data taken on Tm${}_2$Ti${}_2$O${}_7$. The key idea is that the hyperfine interaction, usually neglected in treatments of electronic magnetism, provides a route in which excited states can be mixed into the ground state, and this new state can couple to the "quantum muon'' [1]. This mechanism lies behind the effect found in some quantum spin ice compounds [2], but here it is not based on the distortion effects surrounding the muon. We will show how this idea can be extended to understand the way muons couple to a variety of systems exhibiting highly frustrated magnetism, as well as to dynamical problems more generally [3].

[1] S. J. Blundell, J. Phys.: Conf. Ser. 2462, 012001 (2023).
[2] F. R. Foronda, F. Lang, J. S. Möller, T. Lancaster, A. T. Boothroyd, F. L. Pratt, S. R. Giblin, D. Prabhakaran and S. J. Blundell, Phys. Rev. Lett. 114, 017602 (2015).
[3] S. J. Blundell et al., in preparation.

Speaker: Stephen Blundell (University of Oxford)

musr2025-hyperfine-enhancement.pdf

17 Exploring Topological Magnetic Excitations with Combined μSR, Muon Site Calculations and Simulation¶

An important theme in magnetism is the understanding of phenomena in reduced dimensions using topology. Examples include excitations such as walls, vortices, merons and skyrmions, which exist in the spin textures of a range of systems [1]. Here we discuss case studies from our recent work, emphasising the ways in which muon site calculations, material simulation and $\mu$SR data can be combined to provide insights into the underlying interactions, magnetic phases and dynamics in topological materials.

1) In the multilayer system [Ta/CoFeB/MgO]${}_{16}$/Ta, micromagnetic simulation and low-energy $\mu$SR provide evidence for a change from Néel- to Bloch-like skyrmions with depth into the material [2].
2) In the bulk centrosymmetric skyrmion host Gd${}_2$PdSi${}_3$ [3] single-crystal data and site calculations imply a prominent role for anistotropy in stabilizing skyrmions, while in related GdRu${}_2$Si${}_2$ [4], zero-point fluctuations determine the muon site and measurements suggests RKKY interactions lead to a skymion phase.
3) Finally, recent work on the toplogical-excitation hosting N${}_{1/3}$NbS${}_2$ series provides evidence for phase separation and dynamic transitions, and shows the role of electronic structure in the series.

[1] T. Lancaster, Contemp. Phys. 60, 246 (2019).
[2] T.J. Hicken et al., Phy. Rev. B 109, 134423 (2024).
[3] M. Gomilsek et al., Phys. Rev. Lett. 134 046702 (2025).
[4] B.M. Huddart et al., Phys. Rev. B 111, 054440 (2025).

Speaker: Tom Lancaster (Durham University)

TomLancaster-Mon.pdf

18 Mn Antisites and Order-Disorder Transition in the (MnBi2Te4)(Bi2Te3)n Magnetic Topological Insulators¶

Intrinsic magnetic topological insulators from the MnBi₂Te₄·(Bi₂Te₃)ₙ family have garnered significant attention as versatile platforms capable of hosting a range of exotic quantum states and phenomena, including higher-order topological phases, axion electrodynamics, and the quantum anomalous Hall effect. This tunability arises from manganese–pnictogen intermixing, which is sensitive to synthesis conditions.
In this work [1], we use nuclear magnetic resonance and muon spin rotation and relaxation spectroscopy complemented by DFT calculations to explore the impact of the intermixing on the magnetic properties of (MnBi2Te4)(Bi2Te3)n and MnSb2Te4. Our findings show that Mn moments on native sites and antisites align oppositely in the ground state for (MnBi₂Te₄)(Bi₂Te₃)ₙ (n = 0, 1, 2) and MnSb₂Te₄. Moreover, in all compounds, the Mn antisite sublattice disorders at temperatures significantly below the intrinsic magnetic transition, giving rise to an intermediate phase with a uniform magnetic structure unaffected by intermixing. This phase is likely where the anticipated exotic quantum states can be observed. Our results provide a microscopic understanding of the crucial role played by Mn-Bi intermixing and offer pathways for understanding the surface gap states.

Reference
[1] M. Sahoo, I. J. Onuorah et al., Adv. Sci., 11, 34, 2402753, 2024

Speaker: Ifeanyi John Onuorah (Dipartimento di Scienze Matematiche Fisiche e Informatiche Universitá di Parma Parco delle Scienze 7A, Parma I-43124, Italy)

IfeanyiJohnOnuorah_Mon.pdf

10:20 Coffee Break

Oral Contributions¶

Convener: Michael Graf (Boston College)

19 Spin Liquid Properties of a Spin 1/2 Kagome Metal-OrganicFframework Compound¶

The metal-organic-framework compound Cu${}_3$(HOTP)${}_2$ is a small-gap semiconductor containing a kagome lattice of antiferromagnetically coupled $S$=1/2 Cu${}^{\mathrm{II}}$ spins with intra-layer nearest-neighbour exchange coupling $J\sim$ 2 K. The intra-layer $J$ value obtained from calculations using density functional theory is shown to match with the experimental value for reasonable values of the Hubbard U parameter. Muon spin relaxation confirms no magnetic ordering down to 50 mK and sees spin fluctuations diffusing on a 2D lattice. These properties are consistent with the hypothesis of a quantum spin liquid ground state being present within highly decoupled kagome layers. Reduction of the spin diffusion rate on cooling from the paramagnetic region to the low-temperature region reflects quantum entanglement, one of the key properties of a quantum spin liquid. It is also found that the layers become more strongly decoupled in the low-temperature region. Comparison of results for the spin diffusion, magnetic susceptibility and specific heat in the low temperature region suggests close proximity to a quantum critical point and a large density of low energy spinless electronic excitations. A Z${}_2$-linear Dirac model for the low energy spin excitations of the putative quantum spin liquid ground state is found to provide the best match with experiment [1].
1. F. L. Pratt et al, Phys. Rev. Res. 7, 023007 (2025).

Speaker: Francis Pratt (ISIS)

Musr25.pptx

20 Proximal Quantum Spin Liquid in One-Dimensional Spin-1/2 Metal Ti4MnBi2¶

Electronic correlations lead to heavy quasiparticles in three-dimensional metals, and their collapse can destabilize magnetic moments. It is an open question whether there is an analogous instability in one-dimensional systems, unanswered due to the lack of metallic spin chains. Recently, using neutron scattering, we reported a metallic correlated frustrated spin-1/2 chain compound, Ti4MnBi2 [1,2]. Here, we present the positive muon spin rotation and relaxation (μSR), and magnetic susceptibility measurements study of Ti4MnBi2 single crystal. Zero-field μSR measurements revealed a dramatic slowing down of spin dynamics across 2 K, indicating a spin-freezing transition that aligns with the heat capacity and magnetic susceptibility data. In addition, we observed that less than 10% of spins became static. Interestingly, the other ~ 90% of spins in Ti4MnBi2 single crystal fluctuate in a wide frequency window, i.e., between Hz and THz range, mimicking the glassy relaxation. Our results provide a glimpse of how a metallic one-dimensional system tries to order, proving Ti4MnBi2 is very close to a quantum spin liquid.

REFERENCES
[1] Li, X.Y., Nocera, A., Foyevtsova, K. et al. Frustrated spin-1/2 chains in a correlated metal. Nat. Mater. 24, 716–721 (2025).
[2] Pandey, A. et al. Correlations and incipient antiferromagnetic order within the linear Mn chains of metallic Ti4MnBi2. Phys. Rev. B 102, 014406 (2020).

Speaker: Dr Xiyang Li (IOP, CAS / QMI, UBC)

XiyangLi-Mon.pptx

21 Detection of Spin State Ordering Phenomena in Mn(III) Spin Crossover Solids by Muon Spin Relaxation¶

Spin crossover (SCO) compounds are metal-ligand complexes which can easily switch their internal arrangement of electrons in d-orbitals from paired (low-spin) to unpaired (high-spin), by a minor variation in temperature, pressure, magnetic or electric field, or via irradiation. SCO is observed for some metal-organics containing Fe(II), Fe(III), Mn(III) or Co(II) ions, and the switching is associated with bond length changes of up to 0.2 Å in each metal-donor distance due to depopulation/population of anti-bonding orbitals during the electron pairing/unpairing process. SCO with Jahn-Teller ions such as Mn(III) or Co(II) is of particular interest as the Jahn-Teller distortion can be easily injected into or removed from a lattice by any of the perturbations described above.

To date μSR has been used to follow thermal SCO in only a handlful of Fe(II) compounds. We report now our recent results on using μSR to follow SCO in a Mn(III) complex for the first time. We show that multiple structural symmetry breaking transitions along the polar space group sequence: Cc ↔ Pc ↔ P1 ↔ P1(½)[1]can be successfully detected by muon spin relaxation measurements and that the technique also confirms the emergence of domain walls at different temperatures.

[1] V. B. Jakobsen, E. Trzop, E. Dobbelaar, L. C. Gavin, S. Chikara, X. Ding, K. Esien, H. Müller-Bunz, S. Felton, E. Collet, M. A. Carpenter, V. S. Zapf, G. G. Morgan, J. Am. Chem. Soc, 2022, 144, 195-211.

Speaker: Grace Morgan (University College Dublin)

22 Anomalous Temperature Dependence of Local Magnetic Fields in Altermagnetic MnTe¶

Altermagnets are a novel type of magnetic system that has a spin-polarized electric band structure in the absence of a net magnetic moment. Microscopically this arises from two opposite spin sublattices that are connected by a lattice rotational symmetry instead of a simple translation or inversion [1]. A ferromagnetic-like transport response makes these systems particularly interesting for potential device applications [2]. Hexagonal MnTe is a prototypical altermagnet consisting of alternating ferromagnetically ordered Mn layers [3,4]. Importantly, it exhibits the expected strong spin splittings in the electronic band structure [5]. Here we present muon spin spectroscopy ($\mu$SR) measurements on MnTe single crystals and thin films. Surprisingly, below room temperature we observe pronounced anomalies in the depolarization as well as an onset of a second, non-proportionate zero field oscillation frequency. These findings point to a more complex temperature evolution of the local magnetic environment probed by the muon.

Figure: Depolarization rate and local field measured in zero field $\mu$SR. The inset shows the expected altermagnetic structure.

[1] L. Šmejkal et al., Sci Adv. 6, eaaz8809 (2020)
[2] L. Bai et al., Adv. Funct. Mater. 2024, 2409327 (2024)
[3] N. Kunitomi, et al., J. Physique 25, 568 (1964)
[4] D. Kriegner, et al., PRB 96, 214418 (2017)
[5] J. Krempaský, et al., Nature 626, 517–522 (2024)

Speaker: Jonas A. Krieger (Paul Scherrer Institute)

JonasAKrieger_Mon.pdf

12:00 Lunch

Oral Contributions¶

Convener: Jun Sugiyama (CROSS Neutron Science and Technology Center)

23 µ+SR for a Sustainable Society¶

Establishing a sustainable society is one of the 21st century’s grand challenges. A key barrier is the efficient harvesting, storage, and use of clean energy. Addressing this requires developing new generations of functional materials and devices with advanced energy and quantum properties, which in turn demands control over matter at the nanometer, atomic, and subatomic scales.

In this talk, I will show how µ${}^{+}$SR is a unique and powerful technique for probing energy-relevant materials [1,2]. µ${}^{+}$SR provides microscopic insight into ion mobility, electronic properties, and phase behavior, often inaccessible by other methods.

I will illustrate this with our recent studies of ion dynamics in both anode [3] and cathode [4] materials for rechargeable batteries, as well as in hybrid perovskites used in photovoltaics [5]. These findings shed light on key mechanisms affecting device performance and stability.

Finally, I will highlight the muon’s broader role as a quantum probe [6], vital for the future design of sustainable quantum materials and technologies. Through µ${}^{+}$SR, we aim to support the transition from today’s inefficient electronics to next-generation, energy-efficient quantum devices.

[1] Sugiyama, Phys. Rev. Lett. 103, 147601 (2009)
[2] Månsson, Phys. Scr. 88 068509 (2013)
[3] Forslund, Carbon Energy, Accep. (2025)
[4] Nocerino, Sust. Ener. Fuels, 8, 1424 (2024)
[5] Papadopoulos, Adv. Phys. Res. 3, 2300120 (2024)
[6] Sassa, Subm. (2025)

Speaker: Martin Mansson (KTH Royal Institute of Technology)

24 Observation of Na and Li Ion Diffusion in Battery Materials NaCrO2 and LiCrO2 by μSR¶

Sodium ion batteries have been attractive and developed eagerly for practical use as one of post Lithium ion batteries. Battery materials NaCrO${}_2$ and LiCrO${}_2$ share an identical crystal structure: i.e., a two dimensional layered rock-salt type structure. NaCrO${}_2$ shows high performance with a large capacity of 200 mAh in charge/discharge cycles, while LiCrO${}_2$ has a small capacity in a few cycles. To study the difference in the ion diffusion of the two materials, $\mu$SR measurements were performed at ISIS, Rutherford Appleton Laboratory. Although the obtained $\mu$SR spectra showed a dynamic behavior above 250 K in both materials, the hopping rate of Na${}^{+}$ is about three times higher than that of Li${}^{+}$ at 400 K. This is consistent with the electrochemical properties of NaCrO${}_2$ and LiCrO${}_2$.

Speaker: Izumi Umegaki (KEK (High Energy Accelerator Research Organization))

IzumiUmegaki-21July.pptx

25 Operando μSR and SANS Experiments on Battery Materials¶

To address carbon dioxide emissions, battery performance must be improved. Lithium-ion batteries (LIBs) dominate the market, but their limited and geographically concentrated resources have prompted research into sodium-ion batteries (NIB) to replace LIBs [1]. At J-PARC, we employed positive muon spin relaxation (${\mu }^{+}$SR) [2] and small-angle neutron scattering (SANS) [3] in hard carbon, which is a candidate for anodes in NIBs, to measure self-diffusion coefficients ($D^J$) and structural change, respectively. Our investigation of hard carbon revealed a sodium ion $D^J$ of $2.5\times {10}^{-11}$ cm${}^2/s$—lower than lithium in graphite but with small activation energy. The operando cells have developed, and we compared diffusion in Li${}_x$CoO${}_2$ and Na${}_x$CoO${}_2$ systems under operando measurements, finding distinct concentration-dependent behaviors: lithium showed steep changes near $x$ = 1, while sodium decreased linearly with concentration [4,5]. In the presentation, we will also discuss the results of operando SNAS measurements on hard carbon.

[1] N. Yabuuchi et al., Chem. Rev. 114, 11636 (2014).
[2] K. Ohishi et al., ACS Phys. Chem. Au 2, 98, 107 (2021).
[3] K. Ohishi et al., J. Phys.: Conf. Ser. 2462, 0120048 (2023).
[4] K. Ohishi et al., ACS Appl. Energy Mater. 5, 12538-12544 (2022).
[5] K. Ohishi et al., ACS Appl. Energy Mater. 6, 8111-8119 (2023).

Speaker: Kazuki Ohishi (Comprehensive Research Organization for Science and Society (CROSS))

KazukiOhishi-Mon.pptx

26 Operando µSR Experiments on Palladium Hydride¶

Palladium metal is known to be formed as palladium hydride PdH x by the penetration of dissociated hydrogen atoms into the crystal lattice in a hydrogen gas atmosphere, and has been studied extensively from the viewpoint of industrial applications as a hydrogen storage material. On the other hand, it is also known to exhibit superconductivity at high hydrogen concentrations at low temperatures as low as 9K. In particular, experimental results comparing hydrogen and deuterium absorption show that deuterium-absorbed samples exhibit a higher superconducting transition temperature, which is the opposite tendency of the so-called isotope effect that has long been known and has attracted much attention [1].
We have constructed a cryostat and gas handling system for in-situ observation of hydrogen absorption by the operando µSR technique and observed hydrogen in palladium at low temperatures. A hydrogen concentration of x=0.87 can be achieved by absorption at 150 K. The zero-field µSR time spectrum is well fitted by the Kubo-Toyabe function, and the muon spin relaxation rate is in good agreement with the theoretical prediction when hydrogen occupies the octahedral O-site. Furthermore, a comparison with the experimental results for x=0.7 shows that the muon spin relaxation rate increases with increasing the hydrogen concentration.

1. T. Kawae et al., J. Phys. Soc. Jpn. 89, 051004 (2020).

Speaker: Prof. Akihiro Koda (KEK/J-PARC)

AkihiroKoda-Mon.pptx

14:30 Coffee Break

Honorary Session: Professor Toshimitsu Yamazaki¶

Convener: Kenji Kojima (TRUIMF)

27 Tribute to Professor Toshimitsu Yamazaki¶

Farewell to TY presen.pptx

Jess-presentation-Toshi.pdf

28 Extension of Dynamical Kubo-Toyabe Relaxation Function for Refinement of Ion Dynamics Analysis¶

The dynamical Kubo-Toyabe (DKT) relaxation function predicts the time evolution of muon spin polarization under zero and low longitudinal magnetic fields, which is determined by the linewidth $\mathrm{\Delta }$ due to the static distribution of the internal magnetic field $\mathbf{H}(t)$ and its fluctuation frequency $\nu$. One of its important features is that it can clearly distinguish two causes of decreasing linewidth in transverse-field muon spin relaxation (TF-µSR) that are hardly discernible: changes in the static field distribution (e.g., due to muon site change) and that associated with $\nu$ (motional narrowing) [1]. This is a powerful feature in the study of muon diffusion in metals, and the decrease in the linewidth at low temperatures observed in TF-µSR experiments has been identified as an effect of fluctuations due to quantum diffusion of muons [2].
On the other hand, the success of the DKT function in muon diffusion studies has seemingly created the misconception that the DKT function has proven to be applicable regardless of the source of fluctuations in $\mathbf{H}(t)$. It must be stressed here that every phenomenology including the DKT model has preconditions with which it can be applied: the dynamical model underlying the DKT function requires that the autocorrelation $⟨\mathbf{H}(0)\mathbf{H}(t)⟩$ is entirely lost as $\propto \exp (-\nu t)$. Noting that this condition is non-trivial for the muons subjected to the local dynamics of ions in solids which has been the focus of much research in recent years [3], we have extended the DKT model to the case where only a part of $\mathbf{H}(t)$ fluctuates [4,5]. In this presentation, we discuss how this new phenomenology provides not only a means for quantitative analysis based on the assumption of immobile muons, but also a way to evaluate the validity of this assumption. We may also refer to the similar extension of relaxation model for muonium and muonated radicals that allows discerning the causes of fluctuations for the hyperfine and/or nuclear hyperfine fields [6].

References
[1] R. S. Hayano, et al., Phys. Rev. B 20, 850 (1979).
[2] C. W. Clawson et al., Phys. Rev. Lett. 51, 114 (1983).
[3] See, for example, M. Månsson and J. Sugiyama, Phys. Scr. 88, 068509 (2013).
[4] T. U. Ito and R. Kadono, J. Phys. Soc. Jpn 93, 044602 (2024).
[5] Plugin software for musrfit is available; see https://github.com/tuito0/musrfit-dynGssEALF
[6] R. Kadono and T. U. Ito, arXiv:2410.23575.

Speaker: Ryosuke Kadono (KEK)

RyosukeKadono-21Jul2025(Mon).pptx

29 Negative Muon Beam at D-Line MUSE J-PARC¶

The D-line of the J-PARC MLF MUSE has a pion decay section, which provides access to decay muons in addition to surface muons. The y-superconducting solenoid magnets used in the pion decay section have a large aperture and warm bore, allowing them to guide a wide range of positive and negative muons from high to very low momentum. In addition, the world's highest proton energy of 3 GeV makes negative pion generation particularly efficient. Hence, the world's highest negative muon intensity is achieved.
In recent years, the proton beam output of the MLF has reached 1 MW, and in the D1 area, where the μSR spectrometer is installed, and in the D2 area, where users can install their own equipment including negative muon particle analysers, negative muon spin rotation and relaxation methods, negative muon lifetime measurements, and even elemental negative muon X-ray analysis using negative muon X-rays.
Until now, the profile of the negative muon beam in D1 has been broadened. Various commissioning efforts have been carried out to produce a higher quality beam [1]. As a result, beams with low background and good parallelism have been successfully obtained. In this presentation, the status of beam commissioning in the D-line will be presented.

Speaker: Soshi Takeshita (KEK IMSS Muon)

SoshiTakeshita-Mon_21st_Dline_forupload5.pptx

30 Yamazaki Prize Talk: muSR with Toshi Yamazaki; birth, present and future (Kanetada Nagamine)¶

2507TYprizeTalkused [自動保存済み].pptx

Social Program: Welcome Reception¶

Social Program: "The Resilience of Newfoundland Seabirds in Their Changing Ocean Habitat" (Bill Montevecchi, Memorial University of Newfoundland)¶

31 The Resilience of Newfoundland Seabirds in Their Changing Ocean Habitat¶

Bill Montevecchi is a Professor Emeritus and John Lewis Paton Distinguished University Professor [Psychology, Biology, Ocean Sciences] at Memorial University of Newfoundland and Labrador. Working closely with fishermen, he and his students study birds as indicators of environmental change. Conservation is a priority with research projects aimed at bird interactions with marine and terrestrial energy developments, light pollution, fishing, climate change and recently the avian H5N1 influenza. Ongoing research projects focus on the responses of seabirds to human-created light, on the effects of seabird bycatch in fishing gear and of avian influenza H5N1 and. He invests considerable time communicating evidenced-based scientific information via media presentations and community outreach. See Land & Sea: Safeguarding seabirds | CBC.ca

Tuesday, 22 July ¶

Facilities¶

Convener: Dr Gerald Morris (TRIUMF)

32 PSI Laboratory for Muon Spin Spectroscopy Report¶

Speaker: Thomas Prokscha (Paul Scherrer Institute)

ThomasProkscha_Tuesday.pptx

33 TRIUMF CMMS Facility Update¶

The current and foreseeable status of the TRIUMF Centre for Molecular and Materials Science experimental facilities will be presented. The new M9A and M9H beam lines will be highlighted ... which provide a high flux surface beam and an arbitrarily spin polarized decay beam respectively.

Speaker: Dr Sydney Kreitzman (TRIUMF)

MuSR 2025 TRIUMF CMMS Facility St. Johns.pdf

MuSR 2025 TRIUMF CMMS Facility St. Johns.pptx

34 JPARC Muon Science Facility Report¶

Speaker: Dr Akihiro Koda (J-PARC MUSE)

AkihiroKoda-Tue.pptx

35 ISIS Muon Facility Report¶

Speaker: Adrian Hillier (ISIS Neutron and Muon Facility)

ISIS Update MUSR2025.pptx

36 Status of MuSIC-RCNP Muon Facility¶

The MuSIC muon beamline at RCNP, University of Osaka provides a continuous muon beam with the K140 and K400 cyclotron accelerators. The employment of large capture solenoid magnets and a long cylindrical production target facilitates the utilization of high-intensity muon beams. The first muon beam was observed in 2012, and then user experiments were conducted between 2016 and 2019. However, the beamline was deactivated due to an extended shutdown for maintenance of the K140 AVF cyclotron accelerator and the failure of the solenoid magnets. Repairs to the solenoid have been completed in March 2025. The beam commissioning has recently been conducted for a novel user experiment plan.
Muon beams at MuSIC are utilized for a variety of purposes, including the analysis of muon-induced X-ray emission, nuclear physics allowing for the evaluation of muon-induced nuclear reactions, verification of semiconductor soft errors induced by cosmic-ray muons, and mSR to date. The most active application is non-destructive elemental analysis, including the study of meteorites, the investigation of archaeological materials, and other analytical studies. Moreover, a beam transport simulation has been initiated with the objective of upgrading the beamline to further enhance experimental use.
The presentation will introduce the present status of the facility and provide a brief overview of the experiments to date. It will also include plans for future improvements to the equipments and beamlines.

Speaker: Dai Tomono (Osaka University)

MuSICRCNP_muSR2025_tomono20250722.pdf

10:20 Coffee Break

Facilities¶

37 Design and Prospect of the Muon Source at CSNS¶

A Muon station for sciEnce, technoLOgy and inDustrY (MELODY) project has started construction in the beginning of 2024 at China Spallation Neutron Source (CSNS). A stand-alone target station is designed to produce pions and muons.Three muon beamlines are designed for various applications, including a surface muon beam, a dedicated negative muon beam and one decay muon beamline. A muSR spectrometer is designed with 3024 detectors. In this report, we describe the design of MELODY and prospect for future applications.

Speaker: Lei Shu (Fudan University)

muSR2025(1).pptx

Oral Contributions¶

Convener: Peter Baker (ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory)

38 Depth-Resolved μSR Using Ultra-Slow Muons at J-PARC MUSE¶

At the U-line in J-PARC MLF MUSE, ultra-slow muons (USM) are generated by laser ionization of thermal muonium (Mu) in vacuum. Mu drifts in vacuum with a Maxwellian velocity distribution reflecting the production target temperature; consequently, the USM obtained from Mu ionization are also possess correspondingly low energies. At the U-line, a high-temperature tungsten target (2000 K, corresponding to 0.2 eV) and a room-temperature silica aerogel (300 K, 25 meV) are used. These USM are focused and accelerated by electrostatic lenses and transported to the experimental areas. In the U1A experimental area, a muon spin spectrometer is installed. The implantation energy of muons into the sample can be controlled in the range of sub-keV to 30 keV by adjusting the voltage of a high-voltage stage on which the entire spectrometer is mounted. Whereas surface muons with an energy of 4 MeV, commonly used in materials science research, are suitable probes for bulk samples, USM are well-suited for measurements on thin film samples or near interfaces within materials. We successfully implanted muons selectively into a platinum layer (20 nm thickness) sandwiched by silica layers (10 and 40 nm thicknesses), as reported at the previous μSR2022 conference. In this study, depth-resolved measurements were performed by scanning the beam implantation energy. This contribution will present demonstration results of USM-μSR measurements on multilayer thin film samples.

Speaker: Sohtaro Kanda (KEK)

USM-20250722-MuSR2025.pdf

39 Transmission Muon Microscopy and Scanning μSR Microscopy¶

Muon microscopes [1-3] under development at J-PARC are reported. The transmission muon microscope (TμM) is an analog of a transmission electron microscope (TEM). By employing the strongest penetration power of muons into materials, the TμM allows us to visualizes the 3-dimensional distribution of electromagnetic field in objects much thicker compare to TEMs. This capability is useful to improve power-devices, such as power-semiconductor devices, RF-semiconductors, ceramic capacitors, magnets, piezo-devices, and so on by visualizing their internal electric- or magnetic- fields. We are constructing the 5MeV TμM which employs a muon-cyclotron to accelerate ultra-slow muon-beam to 5 MeV. One of the key technologies is a muon-beam-cooling to increase brightness of the beam. We are constructing a multi-step beam cooling system which produces polarized muon-beam that can be focused into a 30 nm spot. As an application of it, we are also developing a scanning muon spin rotation microscope (SμSRM) which is an analog of the scanning electron microscope (SEM). By measuring the μSR-spectrums point by point, the SμSRM maps the μSR-spectrums in three dimensions with a resolution of 30 nm.

References:
[1] Y. N., Kotaibutsuri 55(6) (2020), p.231-244.
[2] Y. N., Y. Miyake, Isotope News 773, (2021), p.31-36.
[3] Y. N., K. Shimomura, J. Cryst. Soc. Jpn. 65 (2023) p.33-41.

Speaker: Prof. Yukinori Nagatani (KEK IMSS)

YukinoriNagatani-Tue.pptx

40 Advanced Muon-Spin Spectroscopy Using Si-Pixel Detectors - A New Dawn for μSR¶

Muon Spin Relaxation measurements at continuous sources have stagnated at a stopped muons rate of 40 kHz and generally require sample sizes of at least 5 mm by 5 mm. Taking advantage of recent developments in pixel detector technology, we successfully implemented a prototype Si-pixel-based muon spin spectrometer at PSI. Unlike scintillator-based systems, this spectrometer utilizes the MuPix11 chip (≤100 μm thick), enabling tracking with high spatial resolution of 23 μm. The spectrometer is configured as a four-layered telescope, each with an active area of 4 cm by 4 cm, forming two layers upstream of the sample and two downstream. Both muons and positrons are tracked and extrapolated to the sample region. Each muon is matched to an emitted positron if their tracks intersect at the sample position. This spectrometer allows us to go beyond the 40 kHz stopped muons rate generating spatially resolved μSR spectra with low uncorrelated background.

We demonstrate the capabilities of this spectrometer by mapping the magnetic field produced by two NdFeB magnets mounted on a silver plate; see Figure. We are able to extract individual μSR spectra from areas of 1.5 mm by 1.5 mm, thus producing a 2D field map. Additional performance advantages include measurements on multiple samples simultaneously, three-dimensional surface tomography, and unprecedented resolution of submillimeter features in the measured samples.

Speaker: Pascal Isenring (Paul Scherrer Institute)

PascalIsenring-Tue.pdf

12:00 Lunch

Invited Contributions: Invited 2¶

41 Unconventional Superconductivity: Mechanisms for Time-Reversal Symmetry Breaking¶

Unconventional superconductivity is often referred to as originating from a pairing mechanism different from electron-phonon interactions and connected to an anisotropic superconducting order parameter with sign change of the Cooper pair wavefunction. A common microscopic mechanism discussed in view of high temperature superconductors is the spin-fluctuation mediated pairing where the formation of Cooper pairs is possible by avoiding the repulsive Coulomb interaction in space. This effective momentum-dependent pairing interaction gives rise to competing superconducting instabilities with sign-changing and momentum dependent electron pairing. Pinpointing the pairing state in real materials includes to determine of the spin structure of the Cooper pairs, identify possible sign changes of the gap function and detect possible time-reversal symmetry breaking (TRSB).
In this talk, I will review concepts for unconventional pairing, present considerations to investigate the sign of the superconducting order parameter and survey different theoretical mechanisms for the generation of TRSB in superconductors. In cases where a TRSB complex combination of two order parameter components is realized, defects, dislocations and sample edges may generate superflow patterns that can be picked up by magnetic probes. However, even single-component condensates that do not break time-reversal symmetry in their bulk phases can also support signatures of magnetism inside the superconducting state.

Speaker: Andreas Kreisel (Niels Bohr Institute, University of Copenhagen)

Kreisel_Unconventional_SC_TRSB_Tue.pdf

Oral Contributions¶

Convener: Stephen Blundell (University of Oxford)

42 Time-Reversal Symmetry Breaking Superconductivity in HfRhGe: A Noncentrosymmetric Weyl Semimetal¶

Unconventional superconductors offer pathways to novel technologies and deeper insights into electron correlations in condensed matter. Noncentrosymmetric superconductors, lacking inversion symmetry, exhibit mixed spin singlet/triplet pairing, making them candidates for time-reversal symmetry (TRS) breaking in their superconducting states.
We have identified HfRhGe, a new noncentrosymmetric Weyl semimetal with strong SOC, spontaneously breaks TRS in its superconducting state [1]. Magnetization and thermodynamics confirm bulk superconductivity. Zero-field μSR shows TRS breaking. Transverse-field μSR and specific heat indicate a fully gapped state. Calculations reveal Weyl nodes and Fermi arcs, confirming its Weyl semimetal nature. Ginzburg-Landau analysis suggests typical TRS-breaking states have nodes, contradicting our findings. We propose a loop supercurrent state with spontaneous Josephson loops to explain the fully gapped, TRS-breaking phase.
HfRhGe combination of noncentrosymmetry, Weyl topology, strong SOC, and TRS breaking makes it ideal for studying topology and unconventional superconductivity. Its properties suggest potential for the superconducting diode effect, promising quantum device and dissipationless electronics applications.

References:
1: Advanced Materials 37, 2415721 (2025)

Speaker: Adrian Hillier (ISIS Neutron and Muon Facility)

Weyl Semiconductor.pptx

43 To Be or Not To Be: Time-Reversal Symmetry Breaking Superconductivity in Sr2RuO4¶

After three decades of research, the symmetry of the superconducting state in Sr2RuO4 is still under strong debate (1). The long time favoured spin-triplet px + i py state is ruled out by NMR experiments (2). However, in general time-reversal-symmetry breaking (TRSB) superconductivity indicates complex two-component order parameters. Probing Sr2RuO4 under uniaxial pressure offers the possibility to lift the degeneracy between such components (2). We reported results of muon spin relaxation (μSR) measurements on Sr2RuO4 placed under uniaxial stress (3). We observed a large pressure-induced splitting between the onset temperatures of superconductivity (Tc) and TRSB (TTRSB). Moreover, at high stress beyond the van Hove singularity, a new spin density wave ordered phase is observed. To distinguish between a symmetry protected chiral state (d+id) and non-chiral accidentally degenerated order parameters (d+ig, f+ig) we reported SR studies under symmetry conserving hydrostatic pressure. In these experiment no splitting between Tc and TTRSB is observed (4). In this talk we want to discuss if and how these µSR specific observations can be consistent with proposals of single component sc order parameters deduced from recent thermodynamic observations.

(1) Y. Maeno et al., Nature Physics (20) 1712 (2024)
(2) A. Pustogow, et al., Nature 574, 72 (2019)
(3) V. Grinenko, S. Ghosh, et al., Nat. Phys. (2021)
(4) V. Grinenko, et al., Nat. Comm. (2021)

Speaker: Hans-Henning Klauss (TU Dresden, Germany)

44 Discovery of Charge Order and Time-Reversal Symmetry-Breaking in the Kagome Superconductor YRu3Si2¶

We report the discovery of a remarkably rich phase diagram in the kagome superconductor YRu${}_3$Si${}_2$, uncovered through a unique combination of muon spin rotation, magnetotransport, X-ray diffraction, and density functional theory calculations. Our study reveals the emergence of a charge-ordered state with a propagation vector of (1/2, 0, 0), setting a record onset temperature of 800 K for such order in a kagome system and for quantum materials more broadly. In addition, we observe time-reversal symmetry breaking below $T_2^{\ast }$ $\simeq$ 30 K and field-induced magnetism below $T_1^{\ast }$ $\simeq$ 80 K, indicating the presence of a hidden magnetic state. These transitions are mirrored in the magnetoresistance data, which show a clear onset at 100 K and a pronounced increase below 30 K, ultimately reaching a maximum magnetoresistance of 45$\mathrm{\%}$. Band structure calculations identify two van Hove singularities near the Fermi level, one of which resides within a flat band, suggesting a strong interplay between electronic correlations and emergent orders. At low temperatures, we find bulk superconductivity below $T_{\mathrm{c}}$ = 3.4 K, characterized by a two-gap (s+s)-wave or anisotropic s-wave pairing symmetry. Together, our findings point to a coexistence of high-temperature charge order, tunable magnetism, and multigap superconductivity in YRu${}_3$Si${}_2$, positioning it as a compelling platform for exploring strongly correlated kagome physics.

Speaker: Petr Král (PSI Center for Neutron and Muon Sciences)

Král_muSR_2025_YRu3Si2_final.pptx

14:40 Coffee Break

Oral Contributions¶

Convener: Adrian Hillier (ISIS Neutron and Muon Facility)

45 Non-Destructive Analysis of Bronze Heritages Using Muon Induced X-rays in J-PARC¶

Bronze, an alloy mainly composed of copper with additions of tin and lead, has been used for creating historical cultural artifacts across the world. Analysis of the composition of these artifacts provides important insights into their manufacturing techniques, trade routes, and cultural backgrounds. However, surface degradation due to aging—such as oxidation, copper carbonate formation, and leaching of lead and tin—has significantly altered the surface compositions of these materials. Conventional non-destructive X-ray fluorescence (XRF) techniques are unable to probe sufficiently deep to access unaffected regions. Negative muons generated by accelerators can penetrate materials to depths on the order of millimeters. By measuring high-energy characteristic X-rays emitted following negative muon capture, the elemental composition at original, unaffected depths can be non-destructively revealed. At J-PARC MUSE, non-destructive elemental analysis of cultural heritage materials using high-intensity pulsed muon beams is actively being developed. A hemispherical chamber system equipped with nine germanium semiconductor detectors optimized for high sensitivity at low energies has been designed and operated[1]. This presentation introduces a non-destructive elemental analysis of the bronze dolphins ("Shachihoko") of Nagoya Castle, believed to have been produced during the Edo period, as a case study demonstrating the applicability of this technique.
[1] 10.1007/s10751-024-01885-2

Speaker: Motonobu Tampo (KEK)

muSR2025_tampo_v0.pptx

46 Muon-Induced X-ray Emission (MIXE) at PSI: Technique and Applications¶

Muon-Induced X-ray Emission (MIXE) is a non-destructive analytical technique that combines the unique properties of negative muons with high resolution gamma detectors to perform depth-resolved elemental analysis. At PSI, the Germanium Array for Non-destructive Testing (GIANT) instrument leverages a high-intensity continuous muon beam (15–60 MeV/c) to implant muons at tunable depths (µm to cm scale). The subsequent emission of muonic X-rays during atomic de-excitation provides element-specific fingerprints, with sensitivities at the permille level for most elements in the periodic table [1,2].

In archaeology, the technique facilitated the confirmation of the meteoritic origin of a Late Bronze Age iron arrowhead by precisely measuring the high Ni content of the bulk material [3]. The analysis of a Late Antique knob bow fibula revealed dual bronze alloys: high-Pb cast components and low-Pb forged parts, indicating advanced metallurgical tailoring [4]. In energy materials, MIXE paves the way for operando analyses of batteries, such as studying transition-metal plating on electrodes, which is critical for degradation studies [5].

References

[1] S. Biswas et al., Appl. Sci. 12(5), 2541 (2022)
[2] L. Gerchow et al., Rev. Sci. Instrum. 94, 045106 (2023)
[3] B. Hofmann et al., J. Archaeol. Sci. 157, 105827 (2023)
[4] S. Biswas et al., Herit. Sci. 11, 43 (2023)
[5] F. Quérel et al., J. Mater. Chem. A 13, 2275 (2025)

Speaker: Michael Heiss (Paul Scherrer Institut)

MichaelHeiss-Tue.pptx

Poster Session 1: Poster 1¶

Open Table Discussion - Ion Diffusion in Battery Materials Detected by muSR¶

Program - Ion Diffusion and Muonic X-ray elemental analysis.pdf

Wednesday, 23 July ¶

Invited Contributions: Invited 3¶

47 Nuclear Magnetic Resonance in Correlated Quantum Materials: from Frustrated Magnets to Plutonium¶

In condensed matter physics, designing and understanding quantum materials has been the key to searching for emergent behavior and phases of matter and opening a pathway to use them for energy relevant technologies [1]. In the context of correlated quantum materials often hosting 4f and 5f electrons [2,3], a variety of intriguing physical phenomena appear and attract great attention due to an interplay of the interaction between electrons and a competition between their itinerant and localized nature [4]. In this talk, we will highlight our recent advances in the microscopic understanding of quantum materials primarily based on lanthanide (4f) and actinide (5f) elements using nuclear magnetic resonance (NMR) and quadrupole resonance (NQR) spectroscopy combined with other characterization techniques.
First, we will focus on a few lanthanide materials that have either geometrical frustrations (such as in triangular and kagome lattices) or a dimensional reduction and show a hybridization of 4f-electron moments with conduction electrons [5,6]. Ligand site NMR/NQR will be used to probe the magnetic Ce/Yb ions through (transferred) hyperfine couplings at the ligand sites. Examples will be given as to how NMR can be used to unveil important quantities, ranging from energy scales of hybridization and spin fluctuations to order parameter. Then, we will move to other systems of interest in actinide materials, particularly focusing on plutonium-based materials [4]. Direct actinide (239Pu) NMR as well as ligand site (11B, 13C) NMR are performed in some representative systems, such as insulating PuO2 [7] and PuB4 [8,9] or metallic Pu2C3 [10]. We will show how these techniques can provide unique insight into the electronic and structural details of Pu materials, including electronic correlations and cryogenic accumulation of self-irradiation damage as well as its partial healing by annealing.
[1] S. Paschen and Q. Si, Nature Reviews Physics 3, 9 (2021).
[2] Z. F. Weng, M. Smidman, L. Jiao, X. Lu, and H. Q. Yuan, Rep. Prog. Phys. 79, 094503 (2016).
[3] D. Aoki, K. Ishida, and J. Flouquet, J. Phys. Soc. Jpn. 88, 022201 (2019).
[4] E. D. Bauer and J. D. Thompson, Annu. Rev. Condens. Matter Phys. 6, 137 (2015).
[5] M. M. Bordelon, R. Yamamoto, and M. O. Ajeesh et al, Phys. Rev. B 111, 094401 (2025).
[6] S. Park, H. Sakai, H. Hosoi et al, submitted, arXiv:2506.04563 (2025).
[7] H. Yasuoka, G. Koutroulakis, and H. Chudo et al, Science 336, 901 (2012).
[8] A. P. Dioguardi, H. Yasuoka, and S. M. Thomas et al, Phys. Rev. B 99, 035104 (2019).
[9] S. B. Blackwell, R. Yamamoto, and S. M. Thomas et al, Phys. Rev. B 111, 075152 (2025).
[10] R. Yamamoto, M. S. Cook, and A. R. Altenhof et al, submitted (2025).

Speaker: Dr Michi Hirata (Los Alamos National Laboratory)

Oral Contributions¶

Convener: Hans-Henning Klauss (TU Dresden, Germany)

48 Probing Spin Dynamics in Rare-Earth Triangular Lattices YbZn2GaO5 and NdMgAl11O19¶

A quantum spin liquid (QSL) is a long-sought magnetic state in which strong quantum fluctuations prevent magnetic ordering, allowing spin dynamics to persist at very low temperatures. Rare-earth triangular lattice compounds have proven to be a particularly promising platform to study spin liquid behaviours due to their localised f-orbitals and inherent geometric frustration. We present $\mu$SR studies on two such compounds, YbZn${}_2$GaO${}_5$ and NdMgAl${}_{11}$O${}_{19}$, both of which exhibit both the absence of magnetic ordering and evidence of persistent dynamics down to milli-Kelvin temperatures, as shown by our $\mu$SR measurements. In YbZn${}_2$GaO${}_5$, the spin dynamics display a field dependence consistent with a U1A01 Dirac QSL ground state [1]. In NdMgAl${}_{11}$O${}_{19}$, the strong crystalline anisotropy facilitates the quantum tunneling of Ising spins and AC susceptibility measurements reveal behaviour reminiscent of spin ice pyrochlore compounds [2]. These findings highlight the potential for rare-earth triangular lattices to serve as a versatile platform for realising and studying exotic quantum magnetic states.

[1] H. C. H. Wu, F. L. Pratt, B. M. Huddart, D. Chatterjee, P. A. Goddard, J. Singleton, D. Prabhakaran, S. J. Blundell, arXiv:2502.00130.
[2] J. Snyder, J. S. Slusky, R. J. Cava, and P. Schiffer, Nature 413, 48 (2001).

Speaker: Hank Wu (University of Oxford)

MuSR2025_talk.pptx

49 Magnetic and Charge Density Wave Order in La3Ni2O7, La2PrNi2O7, and La4Ni3O10 as a Function of Pressure and Oxygen-Isotope Substitution¶

Recently, bulk superconductivity has been observed in the layered nickelates La₃Ni₂O₇ and La₄Ni₃O₁₀ under hydrostatic pressure, with transition temperatures of up to 80 K. At ambient pressure, these compounds exhibit intertwined and non-trivial spin-density wave (SDW) and charge-density wave (CDW) orders.

In this work, we present a detailed investigation [1, 2] of the structural, electronic, and magnetic properties of three members of the nickelate family - La₃Ni₂O₇, La₂PrNi₂O₇, and La₄Ni₃O₁₀ - as a function of pressure and oxygen-isotope substitution. Using a combination of μSR, resistivity, specific heat, neutron and x-ray diffraction measurements, we identify CDW, SDW as well as spin reorientation transitions.

Notably, the coupling between charge and spin degrees of freedom varies across the different compounds. Oxygen-isotope substitution selectively affects the coupled SDW and CDW states, highlighting the significant role of magnetoelastic coupling in these materials.

For all compounds, we propose distinct types of complex SDW orders and estimate the ordered moment sizes using DFT+μ calculations in conjunction with magnetic dipole field simulations.

[Fig 1: Our phase diagrams demonstrate the difference in coupling between CDW and SDW orders][fig1]

Figure 1 can be found here: https://drive.switch.ch/index.php/s/y4JH92wtE8tpBOb

[1] R. Khasanov et al., Nat. Phys. 21,430 (2025), arXiv:2503.04400, arXiv:2503.06560, arXiv:2504.08290
[2] I. Plokhikh et al., arXiv:2503.05287

Speaker: Thomas Hicken (PSI Center for Neutron and Muon Sciences CNM, 5232 Villigen PSI, Switzerland)

LaNiO.pptx

50 Contrasting c-Axis and In-Plane Uniaxial Stress Effects on Superconductivity and Stripe Order in La1.885Ba0.115CuO4¶

The cuprate superconductor La2-xBaxCuO4 (x=0.125) is a striking example of intertwined electronic orders, where 3D superconductivity is anomalously suppressed, allowing spin and charge stripe order to develop, in a manner consistent with the emergence of a pair-density-wave state.

Understanding this interplay remains a key challenge, highlighting the necessity of external tuning for deeper insight. While in-plane uniaxial stress enhances SC and suppresses stripe order, the effects of c-axis compression remains largely unexplored. Here, we use μSR and AC susceptibility with an in situ piezoelectric stress device to investigate the spin-stripe order and superconductivity in LBCO-0.115 under c-axis compression. The measurements reveal a gradual suppression of the SC transition temperature (Tc) with increasing c-axis stress, in stark contrast to the strong enhancement observed under in-plane stress. We further show that while in-plane (30-degrees to stripe) stress rapidly reduces both the magnetic volume fraction (Vm) and the spin-stripe ordering (Tso), c-axis compression has no effect, with Vm and Tso exhibiting almost stable behavior up to the highest applied stress. These findings reveal a pronounced anisotropy in the stress response, which will help advance the understanding of the microscopic mechanisms linking stripe order and superconductivity in cuprates.

1. Z. Guguchia et al., Proc. Natl. Acad. Sci. 121, e2303423120 (2024)
2. S.S. Islam et al., arXiv:2503.09236 (2025)

Speaker: Dr Shams Sohel Islam (PSI Center for Neutron and Muon Sciences, Switzerland)

SSI_muSR2025_Talk.pptx

10:20 Coffee Break

Oral Contributions¶

Convener: Roberto De Renzi (Department of Physics and Earth Sciences, University of Parma, IT-43124 Parma, Italy)

51 Muon Knight Shift as a Precise Probe of the Superconducting Symmetry of Sr2RuO4¶

Muon Knight shift measurements are a well-established method for determining pairing symmetries in superconductors, particularly effective for $f$-electron-based heavy fermion superconductors. However, precise measurements remain challenging in $d$-electron-based superconductors such as Sr${}_2$RuO${}_4$, where the Knight shift is intrinsically an order of magnitude smaller.
In this talk, we present high-precision muon Knight shift measurements of superconducting Sr${}_2$RuO${}_4$. We found that using multiple crystal pieces, commonly employed in $\mu$SR experiments, causes a serious problem in an applied magnetic field, due to stray fields from neighboring diamagnetic crystals. Thus, one crystal piece was used in this study. We achieve enhanced sensitivity to subtle frequency shifts across the superconducting transition temperature, $T_c$, by carefully separating the various contributions to the shift. This separation was made possible by measuring the SQUID bulk magnetization of the identical Sr${}_2$RuO${}_4$ crystal used in the muon Knight shift experiments, under very similar conditions. We determine the muon Knight shift of Sr${}_2$RuO${}_4$ in the normal state and confirm a significant reduction below $T_c$, consistent with spin-singlet-like pairing. This result highlights the potential of $\mu$SR as a powerful complementary technique to the established method of nuclear magnetic resonance (NMR) for probing spin susceptibility in superconductors.

Speaker: Hisakazu Matsuki (Kyoto University)

Hisa Matsuki muSR conference Muon Knight shift of Sr2RuO4 20250722.pptx

52 Detecting Nematic Superconductivity via µSR: Theory and Experiment¶

Superconductors that spontaneously break rotational symmetry in their electronic ground state are called nematic superconductors. Cu${}_x$Bi${}_2$Se${}_3$ and CaSn${}_3$ are two notable examples that have been studied extensively. Yet, proving the existence of the nematic superconducting state is challenging. Recent theoretical work predicts that odd-parity nematic SC should exhibit a unique magnetic response to external fields, consisting of skyrmion-stripe chains of spatially separated half-quantum vortices. The interplay of their two length scales, the distance between chains and the separation of skyrmions within a chain, leads to a double-peaked structure in the local magnetic field probability density distribution, very different from the conventional single-peak structure associated with standard vortex lattices.
To date, muon-spin rotation (µSR) is the most effective method to detect this skyrmion-stripe pattern, allowing us to identify the double peak structure by the Fourier transform of the time-dependent µSR polarization. We illustrate this by reporting our recent transverse-field µSR results on high-purity LiFeAs single crystals. Our results reveal a splitting of the SC peak in a 30-mT magnetic field parallel to the c-axis, which persists up to about 6 K. Our discovery supports the occurrence of nematic superconductivity in LiFeAs and provides a new pathways to systematically study this new type of SC.

Speaker: Toni Shiroka (Paul Scherrer Institut & ETH Zurich, Switzerland)

53 Field-Orientation-Dependent Magnetic Phases in GdRu2Si2 Probed with Muon-Spin Spectroscopy¶

Centrosymmetric GdRu${}_2$Si${}_2$ exhibits a variety of multi-$Q$ magnetic states as a function of temperature and applied magnetic field, including a square skyrmion-lattice phase. The material’s behaviour is strongly dependent on the direction of the applied field, with different phase diagrams resulting for fields applied parallel or perpendicular to the crystallographic $c$ axis. Using transverse-field $\mu$SR with fields applied along either the [001] or [100] crystallographic directions, we distinguish between the magnetic phases in this system via their distinct muon response, providing additional evidence for the skyrmion and meron-lattice phases, while also suggesting the existence of RKKY-driven muon hyperfine coupling. Zero-field $\mu$SR provides clear evidence for a transition between two distinct magnetically ordered phases at 39 K [1].

We will also discuss novel techniques related to the computation of muon stopping sites using density functional theory (DFT), that were crucial to our analysis in this study. Notably, by considering the energy barriers for moving between muon sites, and accounting for the zero-point energy of the muon, we were able to determine that there is only a single stable crystallographically distinct site. This muon site was confirmed experimentally, using angle-dependent measurements of the muon Knight shift.

1. B.M. Huddart et al., Phys. Rev. B 111, 054440 (2025).

Speaker: Dr Benjamin Huddart (University of Oxford)

BenjaminHuddart-Wednesday.pptx

ISMS Event: ISMS General Assembly¶

12:00 Lunch

Social Program: Conference Excursion¶

Thursday, 24 July ¶

Oral Contributions¶

Convener: Khashayar Ghandi (University of Guelph)

54 Multi-Quantum Spectroscopy of Anisotropic Muonium¶

Multi-quantum (MQ) spectroscopy allows to selectively probe anisotropic muonium. The principal idea is to resonantly drive MQ spin transitions, for which both the electron and the muon spin flip simultaneously (Fig. 1a). In the high-field limit of the electron spin, such MQ microwave excitations are only possible in presence of hyperfine anisotropy, as demonstrated recently for bond-centered muonium in crystalline Si 1.
Here we extend the approach to systems with random orientation. The first system is SrTiO${}_3$, where a polaronic muonium state has been reported with TF-μSR on single crystals. Using MQ spectroscopy, the presence of this state can also be detected in a powder sample of SrTiO${}_3$ and manifests as a resonance curve recorded in LF mode (Fig. 1b). The second system is the catalytic zeolite framework titanium silicalite (TS-1). A MQ resonance curve was detected successfully at 260 K, which confirms the formation of anisotropic, weakly-coupled muonium and holds promise for further μSR studies that focus on catalytic reactions with TS-1.
Besides these results, we outline extensions of the technique, namely MQ experiments at higher fields and microwave frequencies that have the potential to complement ALC μSR on muoniated radicals.

1 A. Doll et al., arXiv:2503.24023 (2025).

Speaker: Andrin Doll (Paul Scherrer Institute)

pres_musr25.pdf

55 Microwave Spectroscopy of the Muonium State in BeO¶

The remarkable thermal, optical and mechanical properties of beryllium oxide lead to a number of applications, however little is known about the behaviour of hydrogen in BeO, which can be as high as 4% in thin films. We used positive muons as a model for hydrogen. Earlier TF data [1] shows both diamagnetic and muonium states and a large "missing fraction".

We measured the muonium fraction using double electron-muon resonance and a novel design of microwave cell which allows low background "flypast" operation with a small sample. A single narrow resonance line is observed, with no resolved splitting due to nuclear coupling. The muonium fraction is found to be larger than that measured by TF-muSR - also unlike the decrease seen in the TF result, the amplitude increases slightly in the range 300-400K. Measurements with delayed RF pulses showed a small increase in muonium fraction at base temperature at later times.

[1] A. G. Marinopoulos et al., Phil. Mag. 97, 2108 (2017)

Speaker: James Lord (ISIS)

Talk with template v5.pptx

56 Non‑Destructive Depth‑Selective Quantification for Carbon in Steel Using Negative Muon Lifetime Analysis¶

The small amount of carbon in steel (<1%), critical in determining its properties, strongly depends on steel production technology. Destructive methods have been generally used to quantify carbon. Still, non-destructive and bulk analysis methods are required from the perspective of quality control in steel production and the analysis of cultural heritages. We propose a novel method of non-destructively quantifying the bulk carbon content in steel by measuring the muon lifetime. The muon captured in decays into electrons or is absorbed in the nucleus. Most of the stopped muons in steel are captured by iron and decay with a short lifetime (206 ns), while the muons captured by the small amount of carbon present have a long lifetime (2000 ns). This makes it possible to detect iron and carbon sensitively by measuring the muon lifetime. The muon lifetime measurements have been conducted at the D1 area in J-PARC MLF using a large solid angle electron detection system for muSR. The Muon capture probabilities of C/Fe for some standard steel samples were evaluated, and the relationship between C/Fe and the elemental content of C was found to exhibit good linearity. Furthermore, muon irradiations for stacked samples consisting of three types of standard steel plates with different incident muon momentum were conducted, and we demonstrated non-destructive depth-selective carbon quantification with carbon contents of 0.20–1.03 wt% (K. Ninomiya et al., Sci. Rep., 14, 1797 (2024)).

Speaker: Kazuhiko Ninomiya (Hiroshima University)

KazuhikoNinomiya-20250724(Thu).pptx

57 An RF-µSR Study of the 2-Norbornyl Radical in Norbornene¶

Radio-frequency muon spin resonance (RF-µSR) has been used to investigate the temperature dependence of the hyperfine parameters of the 2-Norbornyl radical formed in polycrystalline norbornene. Working at a fixed RF frequency of 170.5MHz, field scans show striking changes in both the resonance line shape and amplitude as the temperature is scanned through the plastic phase, with the signal being lost in the brittle phase. Numerical fitting of the resonance spectra using Quantum [1] have allowed the hyperfine parameters to be determined. Data is compared to previous studies of the exo adduct using spin rotation [2] and avoided level crossing [3] measurements.

As part of the RF development programme at ISIS, we have been investigating the use of pulsed RF methods to manipulate spins to observe spin rotation signals from muoniated radicals. Compared to TF-µSR, pulsed RF techniques have the unique advantage of enabling slowly formed radical species to be measured. As a plastic crystal with internal dynamics, norbornene is an ideal test case. Results are presented demonstrating both a 90° rotation of the muon spin polarisation associated with the muoniated radical, and a clear free precession signal. Results obtained are discussed and the spin relaxation rate compared to data shown in reference 2.

[1] J.S. Lord, Physica B 374–375 (2006) 472–474.
[2] M. Ricco et al, J. Chem. Phys. 86, 4198 (1987)
[3] E. Roduner et al, Ber. Bunsenges. Phys. Chem 93 1194 (1989)

Speaker: Dr Stephen Cottrell (UKRI, Rutherford Appleton Laboratory)

StephenCottrell-Thu.pptx

10:20 Coffee Break

Poster session 2: Poster 2¶

12:00 Lunch

Invited Contributions¶

58 I-1 Chiral Phonons: Phonon Angular Momentum and Intrinsic Magnetism¶

Chirality — the geometric property defining the handedness of an object — is a fundamental concept with broad relevance across scientific disciplines. Recent advances have highlighted the pivotal role of chirality in condensed matter physics, particularly through the emergence of chiral phonons: vibrational excitations that carry angular momentum. These quasiparticles are of great interest due to their intrinsic magnetism, which enables non-trivial coupling between lattice vibrations and spin degrees of freedom in solids.
In this presentation, I will show our recent work demonstrating the existence of chiral phonons in non-centrosymmetric crystals, using resonant inelastic X-ray scattering (RIXS) as a probing technique [1,2]. By exploiting the angular momentum transfer between circularly polarized X-ray photons and chiral phonons, we uncover the selection rule that enables the observation of circular contrast in phonon excitation spectra, which is a clear signature of chiral phonons. I will also outline our ongoing efforts to directly detect and characterize the intrinsic magnetism associated with these chiral lattice excitations.

[1] H. Ueda et al., Nature 618, 946-950 (2023).
[2] H. Ueda et al., arXiv 2504.03330.

Speaker: Hiroki Ueda (Paul Scherrer Institute)

muSR2025.pptx

Oral Contributions¶

Convener: Tom Lancaster (Durham University)

59 Revealing the Superconducting Gap Structure in Kagome Metals via μSR and Complementary Techniques¶

The kagome lattice has attracted significant attention in the condensed matter community due to its rich sequence of emergent quantum phases, including chiral charge order, nematicity, superconductivity, and the anomalous Hall effect. Theoretical studies predict that these materials may host unconventional superconducting states, such as chiral superconductivity, making the experimental determination of the superconducting gap structure a critical objective. Muon spin rotation ($\mu$SR) is a powerful technique for probing both the superfluid density and the symmetry of the superconducting gap deep within the bulk of a material. Here, I will present our recent efforts [1-5] to uncover the nature of superconductivity in the kagome compounds AV${}_3$Sb${}_5$, highlighting insights gained from μSR, ARPES, and STM, in combination with external tuning parameters such as chemical doping and applied pressure. Our experiments offer a growing body of evidence that points toward the possibility of unconventional superconductivity in this fascinating class of materials.

[1] C. Mielke III, et. al., and Z. Guguchia, Nature 602, 245 (2022).
[2] Z. Guguchia et. al., Nature Communications 14, 153 (2023).
[3] Z. Guguchia et. al., NPJ Quantum Materials 8, 41 (2023).
[4] J.N. Graham et. al., and Z. Guguchia, arXiv:2411.18744 (2024).
[5] H. Deng, Z. Guguchia et. al., Nature Materials 23, 1639 (2024).
[6] Y. Zhong, J. Liu, Z. Guguchia et. al., Nature 617, 488 (2023).

Speaker: Dr Jennifer Graham (PSI Center for Neutron and Muon Sciences CNM, Switzerland)

60 Towards Fluctuating Magnetism in Zn-Doped Averievite with Well-Separated Kagome Layers¶

The mineral averievite Cu5V2O10(CsCl) possesses a different structure compared to herbertsmithite and other Cu-based kagome spin liquid candidates. The kagome layers are separated by two spacer layers, instead of one in herbertsmithite, reinforcing the 2D character.

The pristine averievite is known to order magnetically at 24 K due to Cu2+ magnetic interlayers but these can be replaced selectively by non-magnetic Zn2+, thus magnetically decoupling the kagome layers [1]. This gives access to an idealized kagome system as well as a tuning parameter to control the three-dimensionality. While only x<1.25 compounds have been reported in the literature, we were able to produce samples with x=2 [2].

We present a MuSR study for x ranging from 0 to 2 [3]. While we confirm the long-range magnetic order in the parent compound (x=0) below 24 K, we clearly show that only a full substitution of inter-plane copper ions (x=2) leads to a quantum-disordered ground state. The experiments performed on the partially substituted material (x=1) uncover that the transformation proceeds through an intermediate frozen disordered ground state. The end compound x=2 thus opens a new avenue to study kagome quantum spin liquids and we will discuss our findings with respect to other existing Cu-based kagome systems.

[1] A.S. Botana et al, PRB 58, 054421 (2018)
[2] M. Georgopoulou et al., arXiv2306.14739 (2023)
[3] G. Simutis et al., arXiv:2504.20871 (2025)

Speaker: Gediminas Simutis (Paul Scherrer Institute)

GediminasSimutis_Thursday.pptx

61 Anomalous Muon Dynamics in Multifunctional Antiferromagnet MnTe¶

The antiferromagnetic semiconductor MnTe has recently attracted enormous research interest. Among other distinctions, MnTe has significance as a leading example of altermagnetism, a high-performance thermoelectric compound when lightly doped, and a platform for spintronics based on antiferromagnetic domains. Muon spin relaxation/rotation (µSR) studies of MnTe can help provide a more complete picture of the magnetism in MnTe, which underlies virtually all of the multifunctional properties of this fascinating compound. We report a comprehensive µSR investigation of pure and Li-doped MnTe. The asymmetry shows unusually complex behavior as a function of temperature: Upon cooling from TN = 307 K to 2 K, we observe the appearance, subsequent disappearance, and ultimate reappearance of up to four distinct precession frequencies. In addition, for intermediate temperatures between approximately 40 K and 100 K, we observe a nearly instantaneous depolarization of the muon ensemble, resulting in the complete loss of asymmetry, which is then fully recovered upon further cooling or warming. With the help of muon stopping site calculations, we explain this striking behavior as a consequence of anomalous muon dynamics in MnTe characterized by thermally assisted hopping among nearly degenerate stopping sites. The results shed light on the magnetic properties of MnTe and highlight the unexpectedly rich behavior associated with muon dynamics.

Speaker: Benjamin Frandsen (Brigham Young University)

Frandsen_MnTe.pptx

14:40 Coffee Break

Oral Contributions¶

Convener: Sarah Dunsiger (TRIUMF / Simon Fraser University)

62 Interfaces of Molecular Magnets and Superconductors¶

Hybrid systems combining superconductors (SCs) with magnetic atoms or molecules have revealed a rich landscape of emergent phenomena, including the formation of localized electronic states at their interfaces, with promising implications for spintronics [1]. In contrast to atomic impurities, magnetic molecules offer chemical tunability, enabling tailored coupling strengths between molecular spins and superconductors [2].
In this contribution, we present results from low-energy muon spin rotation (LE-μSR) experiments on hybrid interfaces comprising molecular magnetic materials (MMMs) deposited on superconducting Nb and Pb thin films. We find that MMMs such as TbPc₂ and CuPc significantly perturb the superconducting state near the interface, as evidenced by modified magnetic field profiles in the Meissner state. These results provide key insight into the nature and spatial extent of magnetic proximity effects in molecular spin–superconductor heterostructures.

[1] Linder J. et al., Nat. Phys., 2015, 11, 307-315.
[2] Hatter, N., et al. Nat Commun., 2015, 6 8988.

Speaker: Dr Zaher Salman (PSI)

Salman-muSR2025.pdf

63 Observation of Charge Carrier Manipulation with Nanometer Depth Resolution at Semiconductor-Oxide Interfaces¶

The manipulation and observation of charge carrier distributions at the interfaces of semiconductor device structures is a fundamental problem in semiconductor physics. Standard electrical characterization techniques, such as deep level transient spectroscopy (DLTS) or capacitance-voltage (CV) measurements, have limited depth resolution and are unsuitable to probe the nanometer scale regions at semiconductor interfaces, where electron and hole transport is directly influenced by changes in applied bias/band bending. We have recently developed an extension to the LE-$\mu$SR setup at PSI that allows us to apply an external electric field across a thin-film sample, while the sample can be floated to ±10 kV to adjust the implantation energy of the muons for performing depths scans. With this “Electric-field-LE-$\mu$SR” (EF-LEM), we were able to observe for the first time the change in electron concentration in Si/SiO${}_2$ and 4H-SiC/SiO${}_2$ structures with nanometer depth resolution, which can be controlled by the EF. We use the muonium state in the semiconductors as a sensitive probe for the presence of free charge carriers and extract their depth distribution [1].

[1] M. Martins et al., arXiv:2405.18211

Speaker: Thomas Prokscha (Paul Scherrer Institute)

ThomasProkscha_Thursday.pptx

Social Program: Pre-Banquet Reception & Banquet¶

Friday, 25 July ¶

Oral Contributions¶

Convener: Graeme Luke (McMaster University)

64 Preformed Magnetic Clusters in the Paramagnetic Phase of a High-Temperature Ferromagnetic Metal-Organic Framework¶

Metal-organic frameworks (MOFs) are composed of metal centres connected by organic polytopic ligands. Their high degree of chemical tunability is reflected in a controlled wide variability of the electronic states, among which magnetism. However, the main drawback against the realization of magnetic phases with high critical temperatures is the weak magnetic coupling between the metal centres provided by the ligands. The recent report of itinerant ferromagnetism with critical temperature $T_C$ = 225 K in the mixed-valent Cr(tri)${}_2$(CF${}_3$SO${}_3$)${}_{0.33}$ (Htri, 1H-1,2,3-triazole) MOF is an exciting development of this field of research in this sense [1].

Here, we report on our extensive investigation of Cr(tri)${}_2$(CF${}_3$SO${}_3$)${}_{0.33}$ by means of ${}^1$H, ${}^{19}$F and ${}^{59}$Co nuclear magnetic resonance and muon-spin rotation [2]. We highlight the lack of any critical dynamics associated with the magnetic transition despite the conventional nature of the long-range ordered configuration detected by muons. The dependence of the spin-lattice relaxation rate on temperature is consistent with the development of activated slow dynamics within the paramagnetic regime. We interpret our results in terms of a disordered phase of segregated magnetic domains akin to what is realized in mixed-valent manganites.

[1] J. G. Park et al., Nature Chemistry, 13, 594 (2021).
[2] G. Prando et al., in preparation.

Speaker: Prof. Giacomo Prando (Dipartimento di Fisica "Alessandro Volta", Università degli Studi di Pavia, Italia)

GiacomoPrando-Fri.pdf

65 Suppression of Antiferromagnetism under High Pressure in Organic Magnet λ-(BEDSe-TTF)2GaCl4¶

The effect of pressure on an organic material is large due to its flexibility, and various physical states such as metal-insulator transition, spin liquid and superconductivity appear. Therefore, systematic research under pressure is important to understand their electronic or magnetic nature. The organic material, $\lambda$-(BEDSe-TTF)${}_2$GaCl${}_4$, is a Mott insulator and antiferromagnetic order appears at ambient pressure below 22 K. In addition, it is suggested that antiferromagnetism is suppressed by pressure. However, the details of the magnetic ground state under pressure are not clear, and we have performed $\mu$SR measurements in $\lambda$-(BEDSe-TTF)${}_2$GaCl${}_4$ under high pressure up to 1.2 GPa at J-PARC.
For high-pressure µSR measurements, we prepared a single-wall Ni-Cr-Al cell or a double-wall Ni-Cr-Al and Cu-Be cell[1]. At ambient pressure, we observed spontaneous muon spin rotation, indicating antiferromagnetic order, in agreement with the previous study [2]. By applying high pressure, the antiferromagnetic component is suppressed and the transition temperature and almost non-magnetic state appear at 1.2 GPa. From these results, it is suggested that the increase of geometric frustration due to pressurization suppresses antiferromagnetism and possible appearance of quantum spin liquid state.

[1] S. Saito et al. submitted to JPS-CP.
[2] A. Ito et al., Phys. Rev. B 106, 045114 (2022).

Speaker: Wataru Higemoto (Advanced Science Research Center, Japan Atomic Energy Agency)

66 CsNiCrF6: A Model System for Studying 1D Spin Dynamics with Muons¶

CsNiCrF${}_6$ is a compound which exhibits multiple coulomb phases: charge ice, displacement ice and spin ice. Having all three of these Coulomb phases ensures that bulk techniques for measuring the dynamics in this compound struggle to grapple with the inherent disorder present [1], and density functional theory calculations on this compound are prohibitively expensive. In this talk, I will provide an in-depth muon study of this compound, showing how the muon site can be determined using the F—$\mu$—F states without needing to resort to DFT calculations, and utilising this to show the 1 dimensional nature of the dynamics of the material using µSR in high longitudinal fields. I will also discuss how our results are strongly supportive of the ‘loop model’ for Heisenberg pyrochlore antiferromagnets, making this compound a model playground for such physics.

[1] T. Fennell et al., Nat. Phys. 15, 60 (2019).

Speaker: John Wilkinson (ISIS Neutron and Muon Source)

MuonConference2025.pptx

10:30 Coffee Break

Oral Contributions¶

Convener: Hubertus Luetkens (Paul Scherrer Institute)

67 μSR study of the multiferroic BiFeO3 at high temperatures¶

Critical phenomena at phase transitions in multiferroic materials remain not fully understood, and quantum beams drive the elucidation of the phenomena from the viewpoint of microscopic dynamical properties. BiFeO${}_3$ is one of the most promising multiferroic materials with high antiferromagnetic ($T_N$$\sim$650 K) and ferroelectric ($T_C$$\sim$1100 K) transition temperatures [1]. We aim to investigate local spin fluctuations in BiFeO${}_3$ to study dynamics near the phase transition in systems with coexisting ferroelectric orderings.
$$ The temperature dependence of initial asymmetry $A_0$ and longitudinal relaxation rate $\lambda$ was obtained by the simple exponential-decay fit in the late time window between 2 and 15 $\mu$s. A sharp increase in $A_0$ and a sudden drop in $\lambda$ are observed at 650 K, indicating the Néel temperature of BiFeO${}_3$. $\lambda$ is a parameter related to the fluctuations of the Fe${}^{3+}$ electron spins. At the high temperature side above $T_N$, $\lambda$ shows a temperature dependence of $T^{1.24}$. On the other hand, at the lower temperature side of $T_N$, corresponding to the ferroelectric–antiferromagnetic ordered phase, $\lambda$ exhibits a non-power-law temperature dependence. This behavior is likely related to underlying electromagnetic coupling in the multiferroic dynamics and/or muon diffusion at elevated temperatures.

[1] P. Fischer et. al., J. Phys. C: Sol. Sta. Phys. 13, 1931 (1980).

Speaker: Hirotaka Okabe (High Energy Accelerator Research Organization (KEK))

HirotakaOkabe-Fri.pptx

68 μSR Observation of Anisotropic Skyrmion and Meron Spin Dynamics in Centrosymmetric Gd2PdSi3¶

Skyrmion lattices (SkLs) are intriguing vortex-like spin textures with non-trivial topology [1,2]. While they are typically stabilized by antisymmetric interactions in bulk noncentrosymmetric materials, centrosymmetric SkL hosts, such as Gd${}_2$PdSi${}_3$ [2–4], have recently been discovered. There, both the SkL stabilization mechanism under applied fields and the zero-field ground states (GSs) remain controversial.

To address these questions, we have investigated the spin dynamics in Gd${}_2$PdSi${}_3$ using µSR [5]. We find highly anisotropic spin fluctuations in its SkL phase [Fig. 1(a)], suggesting a prominent role of anisotropy in SkL stabilization. Intriguingly, we also observe anisotropic dynamics in the GS [Fig. 1(b)], implying that it is a complex meron spin texture, confirming Ref. [4] and refuting other predictions.

Our µSR study Ref. [5] highlights the importance of spin anisotropy even in centrosymmetric SkL hosts and strongly constrains possible SkL stabilization mechanisms.

Fig. 1. Muon relaxation in Gd${}_2$PdSi${}_3$ in (a) the SkL, fanlike (IC-2), and paramagnetic (PM) phases in 0.75 T; and (b) in the meron GS.

[1] T. Lancaster, Contemp. Phys. 60, 246 (2019).
[2] J. Khatua et al., Phys. Rep. 1041, 1 (2023).
[3] S. Li et al., Interdiscip. Mater. 2, 260 (2023).
[4] T. Kurumaji et al., Science 365, 914 (2019).
[5] M. Gomilšek et al., Phys. Rev. Lett. 134, 046702 (2025).

Speaker: Murray Wilson (Memorial University of Newfoundland)

MWilson.pptx

Student Day: Best Oral Presentation¶

Philip_Jones_Student_Day_talk.pdf

Student Day Timetable

Conference Event: Prizes and Closing¶

Thanks.pdf