Phase transformation and magnetic anisotropy of an iron–palladium ferromagnetic shape-memory alloy
by
Cui, J., Shield, T. W., and James, R. D.
in
Acta Materialia, 52(1), pp. 35-47, 2004.
Category: Journal Article
Keywords: ferromagnetic, shape memory, anisotropy
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Abstract:
Martensitic phase transformations in an Fe7Pd3 alloy were studied using various experimental techniques: visual observation, differential scanning calorimeter (DSC) measurements and X-ray diffraction. Magnetic measurements on this alloy were made using a vibrating sample magnetometer (VSM) and a Susceptibility Kappa bridge. The VSM measurements were made with the sample in a compression fixture to bias the martensite phase to a single variant. Both X-ray and DSC measurements show that the FCC–FCT transformation is a weak first-order thermoelastic transition. The average lattice parameters are a =3.822±0.001 Å and c=3.630±0.001 Å for the FCT martensite, and a = 3.756±0.001 Å for the FCC austenite. The latent heat of the FCC–FCT transformation is 10.79±0.01 J/cm3. A Susceptibility Kappa bridge measurement determined the Curie temperature to be 450°C. The saturation magnetization from VSM data is ms =1220±10 emu/cm3 at -20°C for the martensite and ms =1080±10 emu/cm3 at 60°C for the austenite. The easy axes of a single variant of FCT martensite are the [100] and [010] directions (the a-axes of the FCT lattice) and the [001] direction (FCT c-axis) is the hard direction. The cubic magnetic anisotropy constant K1 is 5.2×103 erg/cm3 for the austenite at 60°C, and the tetragonal anisotropy constant K1 + K2 is -3.41±0.02×105 erg/cm3 for the martensite at a temperature of -20°C and under 8 MPa of compressive stress in the [001] direction.
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