It was noted that a significant magnetoresistance effect arose from magnetic field-induced reorientation of martensitic twin variants in a ferromagnetic shape memory Ni50Mn29Ga21 single crystal. The measured electrical resistivity exhibited a large anisotropy and the measured magnetoresistance value was as large as 25% at 230 to 315K in the moderate magnetic field of 1.2T. It was found that a proper combination of the initial state of martensitic twin variants and the direction and magnitude of the applied magnetic field could give rise to either positive or negative magnetoresistance value of ∼25%, thus allowing a periodic modulation of the magnetoresistance effect in response to varying the spatial angle between the directions of applied magnetic field and electric current for every 180°.

Twin-Variant Reorientation-Induced Large Magnetoresistance Effect in Ni50Mn29Ga21 Single Crystal. M.Zeng, S.W.Or, Z.Zhu, S.L.Ho: Journal of Applied Physics, 2010, 108[5], 053716