Investigation of cobalt and silicon co-doping in quaternary Heusler alloy NiFeMnSn

Abstract

Recent study on nearly half-metallic Heusler compound NiFeMnSn pointed out that its high spin polarization was destroyed by the existence of site disorder, hindering its further applications in spintronics devices [Mukadam M D, et al., 2016 Phys. Rev. B 94 214423]. In the present work, by employing the first-principles calculations, we study the influence of Co + Si co-doping on the magnetic properties and electronic structures of NiFeMnSn by substituting Ni with Co as well as Sn with Si. The calculated relative formation energy indicates that the co-doped compound could be easily obtained. The total magnetic moments at various co-doping concentrations are consistent with the Slater-Pauling rule. Analyses on electronic structures reveal that four co-doped compounds, i.e., Ni0.5Co0.5FeMnSn0.25Si0.75, Ni0.5Co0.5FeMnSi, Ni0.25Co0.75FeMnSn0.25Si0.75 and Ni0.25Co0.75FeMnSi possess perfect 100% spin polarization. Furthermore, owing to the fact that the Fermi levels of Ni0.5Co0.5FeMnSn0.25Si0.75, Ni0.5Co0.5FeMnSi and Ni0.25Co0.75FeMnSi are adjusted to the middle of the spin down energy gap, their half metallicity is enhanced.