Ground state and magnetic properties of the Cr-doped Ni-Mn-(Ga, Ge, In, Sn) alloys: Insights from ab initio study

By using first-principles calculations in combination with supercell approach a series of Ni₈Mn₂${\mathrm{Cr}}_2{Z}_4$ (Z = Ga, Ge, In, Sn) are studied with partial replacing of Mn by Cr to investigate the effect of such substitution on their structural and magnetic properties. Two 16-atom supercells with different distribution of Cr in the Mn sublattice and magnetic ordering are considered. Crystal structure optimization shows that the magnetic ground state of Ni₈Mn₂${\mathrm{Cr}}_2{Z}_4$(Z = Ga, In) alloys is the state with pairwise antiparallel magnetic moments of Cr atoms. While for Ni₈Mn₂${\mathrm{Cr}}_2{Z}_4$ (Z = Ge, Sn) alloys is it ferromagnetic state with parallel magnetic moments of Cr and Mn atoms. Based on ground state energies it is shown that martensitic phase can be realized only in Ni₈Mn₂${\mathrm{Cr}}_2{Z}_4$ (Z = Ga, Ge) alloys. For the stable crystal structures with associated magnetic order magnetic exchange constants are calculated, to estimate Curie temperatures with the help of mean-field approximation. Obtained results are in qualitative agreement with experimental and theoretical data.