Thermopower behavior for the shape memory alloy NiTi

We report thermopower measurements for the nickel titanium shape memory all oy Ni0.507Ti0.493. Our measurements reveal abrupt changes in the temperatur e dependence of thermopower, which correlate well with the structural phase transition between the austenitic and martensitic phases. These transition effects in thermopower are more clearly defined than in the resistivity, w hich is also reported. In the martensitic phase, thermopower exhibits stand ard metallic diffusion behavior with a nonlinearity, which is consistent wi th either a small peak in the density of states just below the Fermi level, as calculated by Kulkova, Egorushkin, and Kalchikhin [Solid State Commun. 77, 667 (1991)], or else electron-phonon mass enhancement. For thermally or mechanically treated samples, the magnitude of the transition effects in t hermopower are reduced. (C) 2001 American Institute of Physics.