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Two-dimensional (2D) van der Waals (vdWs) materials have gathered a lot of attention in recent years due to their potential applications for spintronic devices. A big setback with these 2D crystals is their low Curie temperatures T_c < 300 K. As a promising room-temperature vdWs magnet, Fe₅GeTe₂ has gained a lot of attention because of its high T_c of about 270 K[1]. In our work, we synthesized bulk Fe₅GeTe₂ crystals and studied the magnetic properties by temperature-dependent vibrating sample magnetometry (VSM) and ferromagnetic resonance (FMR) techniques. VSM measurements of the bulk Fe₅GeTe₂ sample reveal an in-plane anisotropy with a Curie temperature of 320 K. Thermal capacity measurements show that the sample experiences phase transitions which can be correlated with the changes in magnetism. From the FMR measurements, the gyromagnetic ratio shows a disparity along the in-plane and out-of-plane directions, indicative of orbital momentum contribution. Moreover, the low intrinsic damping indicates a weak intervalley scattering in Fe₅GeTe₂, making it an interesting platform to study spin dynamics.


[1] May et al, Ferromagnetism Near Room Temperature in the Cleavable van der Waals Crystal Fe5GeTe2. ACS Nano 13, 4436 (2019).