Effect of substrate and thickness on polycrystalline hexagonal Fe₂MnSn films grown by magnetron sputtering method

Low-symmetry Heusler alloys are promising materials for next-generation spintronics devices with perpendicular anisotropy. In our prior work, we identified Fe₂MnSn as a promising material with a reasonably high magnetic anisotropy and high Curie temperature. In this work, we present the effect of substrate and thickness on polycrystalline Fe₂MnSn films grown by magnetron co-sputtering. Structure-property analysis uses pole figure x-ray diffraction, magnetoresistance, Hall effect, and Kerr effect measurements. Films grown on c-Al₂O₃ substrate, which has a large lattice mismatch with Fe₂MnSn show a preference for the principle (201) and (200) peak. Films grown on STO(111), which has a good lattice match with the a-b plane of Fe₂MnSn, show a preference for both the (002) and (201) peaks. Pole figure scans on films grown on STO (111) show a six-fold dependence on the phi angle whereas films grown on c-Al₂O₃ and SiO₂ do not show this phi-dependent texturing. Longitudinal and transverse magnetoresistance (MR) appear qualitatively similar, ruling out anisotropic magnetoresistance as a dominant mechanism. Rather, we interpret the peaks in resistance at low fields as evidence of the suppression of spin-flip and grain boundary scattering, and the promotion of large magnetic domains and thus fewer domain walls. Longitudinal Kerr effect measurements show that films with partial (002) texture have higher in-plane magnetization

compared to films with partial (200) texture, consistent with in-plane magnetic anisotropy in films with (002) orientation and out-of-plane anisotropy for (200) films.