Thermal history-dependent physical properties of the two-dimensional ferromagnetic van der Waals Fe_5-xGeTe₂ crystal

Ramesh Yadav^1*, Yung Kang Kuo¹, C. N. Kuo², C. S. Lue²

¹Physics, National Dong Hwa University, Hualien 97401, Taiwan
²Physics, National Cheng Kung University, Tainan 70101, Taiwan

* Presenter:Ramesh Yadav, email:810814301@gms.ndhu.edu.tw

The physical properties of a two-dimensional quenched Fe_5-xGeTe₂ single crystal with x ~ 0.16 were investigated by employing temperature-dependent magnetization, electrical resistivity, and Seebeck coefficient measurement techniques under the sequence of thermal cycling. The physical property measurements show that the Curie temperature, (T_C) ≈ 310-295 K, and the helimagnetic phase, (T_H) ≈ 273 K, are thermal history-dependent. The magnetization examination suggests an itinerant ferromagnetic-like phase, and the easy magnetic axis lies along the c axis while the absolute isotropic features are in the ab plane. The Seebeck coefficient suggests the pronounced transition T* ≈ 100-120 K may be derived from the reconstruction of the Fermi surface. By analyzing electrical resistivity data, it is noted that below transition T*, the electron-electron interactions manifest more strongly than electron-phonon and electron-magnon scatterings. Our findings imply that the magnetic and electrical transport properties of Fe_5-xGeTe₂single crystals are coupled and depend on thermal history.

Keywords: Two-dimensional, thermal-history, Seebeck coefficient