Magnetism and Spin Dynamics in Room-Temperature van der Waals Magnet Fe$_5$GeTe$_2$

TL;DR

This study reports the synthesis and magnetic characterization of Fe$_5$GeTe$_2$, a room-temperature van der Waals magnet, revealing its magnetic properties, damping behavior, and transition from ferromagnetic to ferrimagnetic states, with implications for spintronic applications.

Contribution

The paper presents the first detailed magnetic analysis of Fe$_5$GeTe$_2$ at room temperature, demonstrating its potential for spintronic devices and revealing unique magnetic and damping properties.

Findings

Fe$_5$GeTe$_2$ has a Curie temperature of 332 K.

The material exhibits a sizable Landé g-factor difference indicating orbital contributions.

Fe$_5$GeTe$_2$ transitions from ferromagnetic to ferrimagnetic at lower temperatures.

Abstract

Two-dimensional (2D) 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$_c = 332$ 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$\parallel$c) and the ab-plane (H$\parallel$ab), with temperatures ranging from 300 K to 10 K. We have found a sizable Land\'e g-factor difference between the H$\parallel$c and H$\parallel$ab cases. In both cases, the Land\'e 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.