Payel Chatterjee

FeSn is a room-temperature antiferromagnet composed of alternating Fe3Sn kagome layers and honeycomb Sn layers. Its distinctive lattice allows the formation of linearly dispersing Dirac bands and topological flatbands in its electronic band structure, positioning FeSn as an ideal candidate for investigating the interplay between magnetism and topology. In this study, we investigate the epitaxial growth of FeSn thin films on GaAs(111) substrates by molecular beam epitaxy. A significant challenge in this growth process is the diffusion of Ga and As from the substrate into the deposited films and the diffusion of Fe into the substrate. This diffusion complicates the formation of a pure FeSn phase. Through a comprehensive analysis—including reflection high energy electron diffraction, high-resolution x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and vibrating sample magnetometry—we demonstrate that the Sn evaporation temperature plays a critical role in influencing crystallinity, surface morphology, and magnetic behavior of the films. Our results show that while it is difficult to grow a single-phase FeSn film on GaAs due to diffusion, optimizing the Sn evaporation temperature can enhance the dominance of the FeSn phase, partially overcoming these challenges.

Surface morphology and magnetic properties of ferromagnetic Heusler alloy Co2FeSi thin films and their multi-layers with anti-ferromagnetic Ir50Mn50, which find applications in spintronic devices were investigated. The sputtering process flow for large area deposition of thin films on 3 inch size thermally oxidized single crystal Si(100)/SiO2 substrates have been developed by optimizing the sputtering geometry and other process parameters. A uniform film composition, thickness, smooth surface, good crystallinity and magnetic properties have been achieved in the films over 3-inch size wafers. The isotropic magnetic properties such as saturation/remanent magnetizations, coercivity were achieved in Co2FeSi films deposited on 3-inch size Si(100)/SiO2 wafers with 15 nm Cr buffer layer. An exchange bias anisotropy has been established in Co2FeSi/IrMn multilayer by magnetic annealing process using in-house made magnetic annealing set up. A maximum exchange bias anisotropy field, Hex of 178 Oe and low coercivity, Hc of 85 Oe has been achieved in the Co2FeSi/IrMn multilayer stacks suitable for magnetic tunnel junctions for spintronic applications.