Phase transformation and magnetic properties in Ni 52Fe xMn 21-xGa 27 alloys

Abstract

Effect of chemical composition was investigated on martensitic transformation temperatures, Curie temperature, magnetization for Ni 52Fe xMn 21-xGa 27 alloys. X-ray diffraction patterns revealed that all the samples were in a single Heusler (L2 1) phase state at room temperature. Forward and reverse martensitic transformation temperature, M* and A*, decreased with Fe content, x, up to 15mol% 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 L2 1 phase exhibited intense diffuse streaks on cooling, which were longer than those observed in ternary Ni-Mn-Ga. © 2006 ISIJ.