First-principles investigation of magnetic properties and metamagnetic transition of NiCoMnZ(Z = In, Sn, Sb) Heusler alloys

We employed the density functional theory to investigate the structural, magnetic properties and metamagnetic transition on Mn and Co doped-Ni₂MnZ (Z = In, Sn, Sb) Heusler alloys. The calculated formation energy indicates that excess Mn and Co prefer to occupy Z and Ni sites, respectively. The energy difference between austenite and martensite phases exhibits a monotonic increase with Mn doping, and a decrease with Co doping, which are consistent with the trend of experimental martensitic transformation temperature. The evaluated magnetic exchange parameters show a strong dependence on Z element, which can be explained by the super-exchange interaction mediated by Z sp states near the Fermi level. Bond analysis of martensite phase reveals that the strength of Mn[sbnd]Sb bond is stronger than that of Mn[sbnd]In and Mn[sbnd]Sn bond and it explains the larger driving magnetic field in NiMnSb than NiMnZ(Z = In, Sn) is need for metamagnetic phase transformation. In addition, we predict NiCoMnZ (Z = Sn, Sb) alloys require a smaller compressive epitaxial strain for metamagnetic transition than NiCoMnIn alloys.