Structural, electronic, and magnetic properties of tetragonal Mn/sub3−x/Ga : experiments and first-principles calculations

Abstract

This work reports on the electronic, magnetic, and structural properties of the binary intermetallic compounds Mn3−xGa. The tetragonal DO22 phase of the Mn3−xGa series, with x varying from 0 to 1.0 in steps of x=0.1, was successfully synthesized and investigated. It was found that all these materials are hard magnetic, with energy products ranging from 10.1 kJ m−3 for low Mn content (x→1) to 61.6 kJ m−3 for high Mn content (x→0) . With decreasing Mn content, the average saturation magnetization per atom increases from 0.26 B for Mn3Ga to 0.47 B for Mn2Ga. The increase in the saturation magnetization as the Mn content is reduced indicates a ferrimagnetic order with partially compensating moments of the two different Mn atoms on the two crystallographically different sites of the DO22 structure. This type of magnetic order is supported by ab initio calculations of the electronic structure that predict a nearly half-metallic ferrimagnet with the highest spin polarization of 88% at the Fermi energy for Mn3Ga. The Curie temperature of the compounds is restricted to approximately 770 K because of a structural phase transition to the hexagonal DO19 phase. Thermal irreversibilities between zero-field-cooled and field-cooled measurements suggest that the Mn3−xGa series belongs to the class of magnetically frustrated ferrimagnets. The most pronounced magnetic anomaly is found for Mn3Ga.