Thermally excited spin-current in metals with embedded ferromagnetic nanoclusters

We show that a thermally excited spin-current naturally appears in metals with embedded ferromagnetic nanoclusters. When such materials are subjected to a magnetic field, a spin current can be generated by a temperature gradient across the sample as a signature of electron-hole symmetry breaking in a metal due to the electron spin-flip scattering from polarised magnetic moments. Such a spin current can be observed via a giant magneto-thermopower which tracks the polarisation state of the magnetic subsystem and is proportional to the magnetoresistance. Our theory explains the recent experiment on Co clusters in copper by S. Serrano-Guisan \textit{et al} [Nature Materials AOP, doi:10.1038/nmat1713 (2006)]