Electronic and magnetic properties of quaternary (Cu, Ni)MnSb alloys

Abstract

Magnetic properties and Curie temperatures of semi-Heusler alloys Cu_1−x Ni _x MnSb are calculated as a function of the alloy composition. The transition from the ferromagnetic state (NiMnSb) to the antiferromagnetic state (CuMnSb) gives rise to an abrupt change in the concentration dependence of alloy magnetization at about x _Cu = 0.7 while the Curie temperature decreases monotonically with the Cu-content. Such behaviour can be understood as being due to the onset of disorder in orientations of Mn-spins at x _Cu = 0.7. A simple account of magnetic disorder as based on the uncompensated disorder local moment picture provides also a good quantitative understanding of available experimental data.

Keywords:

• density functional theory
• exchange interactions
• effective Heisenberg model
• magnetic disorder
• Curie temperature
• quaternary Heusler alloys

Acknowledgements

This research was carried out within the projects AVOZ 10100520 and AVOZ 20410507 of the Academy of Sciences of the Czech Republic. The authors acknowledge financial support from the Grant Agency of the Academy Sciences of the Czech Republic (A100100616), the Czech Science Foundation (202/07/0456), and COST P19 (OC150).