Magnetic field-control of microstructure and function of materials exhibiting solid-solid phase transformation

We have investigated effects of magnetic field on transformation temperatures of a pure iron specimen and selection of variants formed by martensitic transformation in an Fe-31.2Pd (at.%) alloy single crystal and disorder-order transition in a CoPt single crystal. Following results are obtained: (i) the equilibrium temperature of austenite to ferrite transformation in the pure iron specimen increases by about 7 K when a magnetic field of 10 T is applied, and the result is discussed on the basis of the Clausius-Clapeyron equation; (ii) the rearrangement of martensite variants driven by magnetic field is confirmed to occur in the Fe-31.2Pd (at.%) ferromagnetic shape memory alloy, and the behavior is discussed quantitatively by introducing magnetic shear stress acting across the twinning plane; (iii) single variant of L10-type ordered phase in a CoPt is obtained by ordering heat-treatment under a magnetic field.