Speaker
Description
Fe$_3$GeTe$_2$ is a quasi-2D itinerant ferromagnet with a Van-der-Waals layered structure that exhibits substantial magnetic anisotropy. In bulk samples, this material becomes magnetically ordered below 200 K, although the low-temperature magnetic state for pure samples is debated, with some data suggesting a succession of two similar ferromagnetic states, and some suggesting a transition between ferromagnetism and antiferromagnetism with temperature. We grew high-quality, pure crystals of Fe$_3$GeTe$_2$ using chemical vapor transport and investigated them using magnetometry and µSR. Magnetometry measurements of our samples shown two transitions, one at 215 K and one at 165 K, consistent with previous reports. Zero field µSR data fits to Kubo-Toyabe behavior across the whole temperature range with additional long-time relaxation, and continuous smooth evolution of the Kubo-Toyabe relaxation rate as a function of temperature that is consistent with 3D Ising behavior. No significant evidence for a second transition to a substantially different magnetic state is seen in this data. Simulations of the ferromagnetic and antiferromagnetic states using MueSR and DFT-based muon site calculations suggest an expected dramatic difference between the muon signature of these states, which is not observed in our data. This suggests that the zero-field magnetic state of Fe$_3$GeTe$_2$ does not transition between ferromagnetism and antiferromagnetism as a function of temperature.
| murray.wilson@mun.ca | |
| Funding Agency | National Sciences and Engineering Research Council, Engineering and Physical Sciences Research Council |
