Electronic, magnetic, and transport properties and magnetic phase transition in quaternary (Cu,Ni)MnSb Heusler alloys

Abstract

The electronic properties, finite-temperature magnetism, and transport properties of semi-Heusler quaternary alloys Cu,Ni MnSb are studied theoretically by means of ab initio calculations as a function of the alloy composition. As documented by experiment, the transition from the ferromagnetic state NiMnSb to the antiferromagnetic state CuMnSb gives rise to an abrupt change in the magnetic moments and resistivities at about xCu 0.7, while the Curie temperature exhibits a smooth behavior with the Cu content. We explain this peculiar behavior with the onset of disorder in orientations of the Mn spins at xCu 0.7. A simple account of magnetic disorder based on the so-called uncompensated disordered local-moment picture provides a good quantitative understanding of available experimental data. An origin of the observed magnetic phase transition is also discussed.\