Influence of temperature on rearrangement of martensite variants by magnetic field in Fe 3Pt

Abstract

We have investigated influence of temperature on magnetic field-induced strain due to rearrangement of martensite variants in Fe 3Pt 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 f P 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 f P obtained by FC process (3.2 MA/m) gradually increase with decreasing temperature while f P 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.