Composition and temperature dependence of the thermoelectric power of Ni_(2+x)Mn_(1-x)Ga alloys

The thermoelectric power (TEP) measurements have been carried out to investigate the changes in the electronic structure associated with the intermartensitic and martensitic transitions in Ni$_{2+x}$Mn$_{1-x}$Ga (0 $\le$ x $\le$ 0.19). The samples have been characterized by a.c. magnetic susceptibility measurements. The correlation between the TEP and the microstructural changes sensitive to the increasing Ni content in Ni$_{2+x}$Mn$_{1-x}$Ga has been investigated. The changes in the density of states as reflected in the temperature variation of the TEP are consistent with the conclusions drawn from the Jahn-Teller mechanism of lattice distortion.