Exploring thermoelectric effects and Wiedemann–Franz violation in magnetic nanostructures via micromachined thermal platforms

We describe the development and use of micromachined thermal isolation structures to explore thermoelectric effects in magnetic thin films and nanostructures. These unique measurement techniques allow fundamental studies that will help enable a wide range of spin-caloritronic devices that take advantage of the coupling between heat and magnetic degrees of freedom for useful effects. The thermal platform is capable of measuring thermal conductivity, kk, thermopower (Seebeck coefficient), αα, and electrical conductivity, σσ, all on the same thin film sample. This also allows direct comparison of the measured thermal conductivity of a magnetic thin film to the prediction of the Wiedemann–Franz law based on measured electrical conductivity. In addition to describing the fabrication of the platforms and the basic principles of their operation, we present example data on nickel and nickel–iron alloy thin films, and briefly consider the range of samples that can be measured with both current techniques and future thermal platforms optimized for nanoscale samples.