A detailed study was made of electrical resistivity variations with temperature at various twin configurations in Ni49Mn29Ga22. It was noted that, in the martensitic region (<300K), the structural transition occurred at 200 to 300K, and measurements were made within that range. By using compressive stresses, various twin configurations of the crystal were obtained. It was found that, during the heating cycle, the alloy underwent an inter-martensitic transformation, M to M’. At around 270K, the resistivity of M’ was some 20% greater than that of M and depended upon the martensite variant distribution. The resistivity did not depend upon the number of twin boundaries present in the crystal, but instead depended upon the crystal orientation with respect to the direction of the current. The temperature of the observed intermartensitic transition was strongly dependent upon the number of twin boundaries, and was found to be lowest when the number of twin boundaries was greatest.

Do Twin Boundaries Affect the Resistivity of Single Crystal Ni49Mn29Ga22 Heusler Alloy? V.K.Srivastava, R.Chatterjee: Journal of Physics D, 2007, 40[16], 4998-5001