Magnetic and Magnetovolume Properties of the Cu₃Au Type Ordered Fe–Pt Alloys around the γ-α Phase Boundary

Abstract

Magnetization, thermal expansion and forced volume magnetostriction have been measured for Fe_1−xPt_x ordered alloys (x=0.23–0.27). In the fcc alloys (x≥0.25), the atomic moment and the spontaneous volume magnetostriction increase monotonically with decreasing x, implying the Fe–Pt Invar alloys to be homogeneous and strong ferromagnets even around the γ-α phase boundary. On the other hand, the magnetic moment of the α phase (x<0.25) is a little larger than that of the γ phase, suggesting a very weak magnetic field dependence of the M_s temperature. The observed large spontaneous volume magnetostriction may play an important role in determining the favorable conditions for the thermoelastic martensite transformation in the Fe–Pt alloys.