Signature of martensite transformation on conductivity noise in thin films of NiTi shape memory alloys

Slow time-dependent fluctuations, or noise, in the electrical resistance of dc magnetron sputtered thin films of nickel-titanium shape memory alloys have been measured. Even in equilibrium, the noise was several orders of magnitude larger than that in simple diffusive metallic films and was found to be nonmonotonic around the martensitic transformation regime. The results are discussed in terms of the dynamics of structural defects, which also lay the foundation to a new noise-based characterization scheme of martensite transformation. (c) 2008 American Institute of Physics.