Characterization of Alloyed Fe_3-xCo_xSn₂ Kagomé-Lattice Films Grown Using Molecular Beam Epitaxy

Materials in which transition metals form a kagomé lattice have generated interest in recent years due to their unique magnetic and electronic properties. Ferromagnetic Fe₃Sn₂ is one such example where the Fe kagomé sublattice results inleads to the presence of Weyl fermions and flat bands. Being able to tune Weyl nodes has been an area of immense study, and hole and electron-doping are a potential avenues for changing the position of Weyl nodes in energy and momentum-space, and as a result, as well as moving the Fermi level with respect to the Weyl pointsthem with respect to the Fermi level. We performed an experimental investigation on[PM1] the effect of electron-doping in epitaxially- grown thin films of Fe₃Sn₂ through substitution of Co for Fe. We have grown Fe_3-xCo_xSn₂ films using molecular beam epitaxy (MBE) at various concentrations of Co (x = 0, 0.1, 0.5, 0.75, 1.0) on Al₂O₃ (0001) substrates buffered with a thin Co (111[SM2] ) wetting[PM3] buffer layer. The Fe_3-xCo_xSn₂ films are capped with CaF₂ to prevent oxidation. Structural characterization of the heterostructures by <i>in situ by </i>reflection high-energy electron diffraction <i>RHEED</i> confirms the growth of ordered films, and further surface characterization via X-ray reflectivity and atomic force microscopy identifies smooth surfaces. X-ray diffraction was used to confirm that the films have uniform <i>c</i>-axis orientation and that no secondary phases are present, while magnetometry was used to study the magnetic properties of the films . Further, it was observed that both the <i>c</i>-axis parameter and saturation magnetization decreases with increasing Co concentration, in agreement with previous density functional theory calculations (M. Adams <i>et al</i> 2023 J. <i>Phys.: Condens.</i> <i>Matter</i> <b>35</b> 265801). [PM4] Magnetometry measurements revealed a decrease in saturation magnetization as the Co content was increased. Our results provide the groundwork for further investigation on the changing magnetic properties and electronic band structure in doped alloyed epitaxial Fe₃Sn₂ heterostructures.<br/><br/>A.W.L. was primarily supported by NSF through the University of Pennsylvania Materials Research Science and Engineering Center (MRSEC) (DMR-1720530).