Phase Transformation and Magnetic Properties in Ni₅₂Fe_xMn_21−xGa₂₇ Alloys

Abstract

Effect of chemical composition was investigated on martensitic transformation temperatures, Curie temperature, magnetization for Ni₅₂Fe_xMn_21−xGa₂₇ alloys. X-ray diffraction patterns revealed that all the samples were in a single Heusler (L2₁) phase state at room temperature. Forward and reverse martensitic transformation temperature, M* and A*, decreased with Fe content, x, up to 15 mol% and then turned to increase by further addition of Fe. Composition dependence of the Curie temperature exhibited a reversed tendency compared with M*. The structure of martensite was 10M for the alloys with x<15 and a mixture of 14M and 10M for x=20. Electron diffraction patterns of L2₁ phase exhibited intense diffuse streaks on cooling, which were longer than those observed in ternary Ni–Mn–Ga.