High spin polarization in the disordered quaternary Heusler alloy FeMnVGa

Abstract

In this paper, we report the successful synthesis of a Fe-based highly spin-polarized quaternary Heusler alloy FeMnVGa and its structural, magnetic, and transport properties probed through different experimental methods and theoretical techniques. Density functional theory (DFT) calculations performed on different types of structures reveal that the structure with Ga at $4a$, V at $4b$, Mn at $4c$, and Fe at $4d$ (space group $F\overline{4}3m$) possess minimum energy among all the ordered variants. Ab initio simulations in the most stable ordered structure show that the compound is a ferromagnet having a large spin-polarization (89.9%). Neutron diffraction reveals that the compound crystallizes in disordered type-2 structure (space group $Fm\overline{3}m$) in which Ga occupies at $4a$, V $4b$ and Fe/Mn occupy $4c/4d$ sites with 50:50 proportions. The structural disorder is further confirmed by x-ray diffraction, extended x-ray absorption fine structure, $^{57}\mathrm{Fe}$ M\"ossbauer spectrometry results, and DFT calculations. Magnetization studies suggest that the compound orders ferromagnetically below ${T}_{\mathrm{C}}\phantom{\rule{4pt}{0ex}}\ensuremath{\sim}293$ K and the saturation magnetization follows the Slater-Pauling rule. M\"ossbauer spectrometry, along with neutron diffraction, suggest that Mn is the major contributor to the total magnetism in the compound, consistent with the theoretical calculations, which also indicates that spin polarization remains high (81.3%), even in the presence of such large atomic disorder. The robustness of the half-metallic ferromagnetic (HMF) property in the presence of disorder is a quite unique characteristic over other reported HMF in literature and makes this compound quite promising for spintronics applications.

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