Magnetic field effect on premartensitic transition in Ni-Mn-Ga alloys

Extensive measurements of the temperature dependencies of resistivity under constant magnetic fields made it possible to clarify the premartensitic transition sensitivity to applied magnetic field up to 14 T in polycrystalline and monocrystalline Ni-Mn-Ga alloys with compositions close to the stoichiometric one. A low-field minimum on the transition temperature versus magnetic field curves is found in both alloys. This minimum is attributed to the magnetic anisotropy contribution to the Clausius-Clapeyron relationship, which describes the premartensitic transition. This contribution is confirmed by magnetization loops measurements.