Antiferromagnetic Transition in γ-Phase Mn Alloys

Abstract

Specific heat measurements on Mn‐rich Mn‐Cu alloys reveal first‐order antiferromagnetic phase transitions at around room temperature and above. Magnetic entropy increases with Mn content but in all alloys it is smaller than would be expected from localized spins. The same is true of an equiatomic FeMn alloy. However the specific heat exhibits a well‐defined cusp at 475°K, indicating a transition of second or higher order. By extrapolating the Mn‐Cu results to pure Mn, the thermodynamic properties of γ‐Mn in the region of the transition are derived.