Influence of temperature on rearrangement of martensite variants by magnetic field in Fe3Pt

We have investigated influence of temperature on magnetic field-induced strain due to rearrangement of martensite variants in Fe3Pt with a degree of order of 0.8. Measurements were made in the field-cooling process (FC) and field application process after zero-field cooling (ZFC), where magnetic field was applied along three principal directions: [0 0 1]P, [1 1 0]P and [1 1 1]P (index are given by the parent phase). From the measured strain and lattice parameters, we evaluated the fraction fP of the preferable variant, which has the lowest magnetic energy among three variants. In the case of the [0 0 1]P and [1 1 0]P fields, the fraction fP obtained by FC process (3.2 MA/m) gradually increase with decreasing temperature while fP obtained by field application process after ZFC shows a maximum value around 40 K. On the other hand, the field-induced strain does not appear for the [1 1 1]P field regardless of both processes. A part of the magnetic field-induced strain is reversible and it shows a maximum value of 1% at 20 K under the [0 0 1]P field.