Epitaxial Growth and Magnetic Properties of Kagomé Metal FeSn/Elemental Ferromagnet Heterostructures

Binary kagomé compounds <i>T_mX_n</i> (<i>T</i>=Mn, Fe, Co; <i>X</i>=Sn, Ge; <i>m</i>:<i>n </i>= 3:1, 3:2, 1:1) have garnered significant interest due to the coexistence of topological band crossings and flat bands stemming from the geometry of the metal-site kagomé lattice. In order to harness these distinctive electronic band features for potential applications in spintronics, it is imperative to grow high-quality heterostructures. In this work, we detail the synthesis of Fe/FeSn and Co/FeSn bilayers on <i>c</i>-axis-oriented Al₂O₃ substrates, achieved <i>via</i> molecular beam epitaxy. The use of elemental buffer layers (Fe and Co) facilitates the growth of smooth and continuous FeSn films, while also enabling the formation of heterointerfaces between elemental ferromagnetic metals and antiferromagnetic kagomé metal FeSn. Structural characterization using high-resolution X-ray diffraction, reflection high-energy electron diffraction, scanning electron microscopy and transmission electron microscopy revealed the FeSn films were flat and epitaxial with well defined interfaces. Rutherford backscattering spectrometry was used to confirm the stoichiometric window where single phase FeSn films are stabilized, while transport and magnetometry measurements were conducted to verify metallicity and magnetic ordering in the bilayers. We observe exchange bias in both bilayer systems, affirming the existence of antiferromagnetic order in FeSn, thus opening possibilities for further investigations into interfacial magnetism in kagomé heterostructures and the potential integration of these materials into spintronics devices.<br/><br/>Work at Drexel University and the University of Illinois at Urbana-Champaign was supported by the National Science Foundation, grant number ECCS-2031870. Work at University of Pennsylvania was supported by University of Pennsylvania Materials Research Science and Engineering Center (MRSEC) (DMR-2309043).