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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).
| higemoto.wataru@jaea.go.jp | |
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