Degenerate Magnetic Structures and Antiferromagnetic Phase Transitions in \gamma--{\rm Mn} Alloys

Abstract

Manganese alloy systems, which have been studied experimentally, show a host of antiferromagnetic phase transitions. Developing a linearized theory for the classical Heisenberg model, we can solve the local distortion of model of spins around an impurity in non--collinear antiferromagnet. Since the alloying removes the degeneracy in non--collinear magnets, this theory is useful. Looking at the case of \gamma--Mn alloys, especially Mn_3Pt, we can predict the experimentally observed phase transitions caused by alloying.