Two-dimensional van der Waals (vdW) materials are materials whose crystal structure features neutral, single-atom-thick or polyhedral-thick layers of atoms with covalent or ionic bonding along two dimensions and van der Waals bonding along the third axis. The weak van der Waals bonding energies ( ̴40-70 meV) enable these 2D materials to be mechanically or chemically exfoliated into a few or single atomic layers. These ultra-thin materials have unique and potentially useful properties, such as high electron mobilities, topologically protected states, tunable band structure and high thermal conductivities etc., which might provide opportunities for spintronic devices and quantum computing [1]. Hence, the family of 2D vdW materials has grown significantly over the last two decades, exploring unusual physical phenomena in two dimensions, creating the possible vdW heterostructures and developing new devices [2]. However, 2D layered crystals with intrinsic long range ordered magnetism were not discovered until 2017 [3, 4]. 2D vdW ferromagnets are of interest as building blocks for heterostructures designed for use in spin-based information technologies because spin-orbit coupling within heterostructures generally yields interesting spin structures and magnetoelectric transport. For practical applications of 2D vdW ferromagnets in the next-generation spintronic devices, it is crucial for 2D materials to have magnetic states that are stable at room temperature [5]. No intrinsic 2D vdW ferromagnetic crystals with a room-temperature Curie temperature (Tc) were found until 2022 when 2D vdW ferromagnetic crystal Fe3GaTe2 was reported, showing Tc up to a record-high ̴ 380K for known intrinsic vdW ferromagnets. These crystals were observed to have high Msat 40.11 emu/g, large perpendicular magnetic anisotropy (PMA) energy density ̴ 4.79 × 105 J/m3, and a large anomalous Hall angle of 3% at room temperature. The PMA energy density of 2D Fe3GaTe2 nanosheet is ̴ 3.88 × 105 J/m3, which is better than some widely-used conventional ferromagnetic films such as CoFeB and Co2FeAl, and one order of magnitude larger than other 2D vdW ferromagnets. The study also reported that room-temperature thickness and angle-dependent anomalous Hall devices based on Fe3GaTe2 nanosheet have been realized, which provides an avenue for next-generation magnetoelectronics and spintronics based on 2D vdW ferromagnetic crystals and various vdW heterostructures [6]. In this poster, we will give the first results of magnetization measurements of single crystal Fe3GaTe2 and magnetic structure information from neutron powder diffraction. Magnetization measurement shows ferromagnetic properties with above-room-temperature Tc (~332-355K) under out-of-plane measurement. Diffraction data from neutron scattering will be analysed via Rietveld refinement, which is still in progress.
About the presenter
Mengyun (Molly) You is a PhD Student at The University of Wollongong with CI Xiaolin Wang and ANSTO AI Kirrily Rule. Her project aims to investigate magnetic properties of ferrofluids, as part of FLEET’s Research Theme 1, Topological Dissipationless.