Magnetism and spin dynamics in room-temperature van der Waals magnet Fe <sub>5</sub> GeTe <sub>2</sub>
Laith Alahmed, Bhuwan Nepal, Juan Macy, Wenkai Zheng, Brian Casas, Arjun Sapkota, Nicholas Jones, Alessandro R Mazza, Matthew Brahlek, Wencan Jin, Masoud Mahjouri-Samani, Steven S.-L. Zhang, Claudia Mewes, Luis Balicas, Tim Mewes, Peng Li
Abstract
Abstract Two-dimensional van der Waals (vdWs) materials have gathered a lot of attention recently. However, the majority of these materials have Curie temperatures that are well below room temperature, making it challenging to incorporate them into device applications. In this work, we synthesized a room-temperature vdW magnetic crystal Fe 5 GeTe 2 with a Curie temperature T <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi/> <mml:mi>c</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>332</mml:mn> </mml:math> K, and studied its magnetic properties by vibrating sample magnetometry (VSM) and broadband ferromagnetic resonance (FMR) spectroscopy. The experiments were performed with external magnetic fields applied along the c -axis ( H <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∥</mml:mo> </mml:math> c ) and the ab -plane ( H <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∥</mml:mo> </mml:math> ab ), with temperatures ranging from 300 to 10 K. We have found a sizable Landé g -factor difference between the H <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∥</mml:mo> </mml:math> c and H <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∥</mml:mo> </mml:math> ab cases. In both cases, the Landé g -factor values deviated from g = 2. This indicates contribution of orbital angular momentum to the magnetic moment. The FMR measurements reveal that Fe 5 GeTe 2 has a damping constant comparable to Permalloy. With reducing temperature, the linewidth was broadened. Together with the VSM data, our measurements indicate that Fe 5 GeTe 2 transitions from ferromagnetic to ferrimagnetic at lower temperatures. Our experiments highlight key information regarding the magnetic state and spin scattering processes in Fe 5 GeTe 2 , which promote the understanding of magnetism in Fe 5 GeTe 2 , leading to implementations of Fe 5 GeTe 2 based room-temperature spintronic devices.