Spin temperature and thermalization in spin valves

We study the concept of spin temperature in excited spin valves, more precisely the effective electron temperature that may become spin dependent, both in linear response and far from equilibrium. A temperature or voltage gradient create non-equilibrium energy distributions of the two spin ensembles in the normal metal spacer, which approach Fermi-Dirac functions through energy relaxation mediated by electron-electron and electron-phonon coupling. Both mechanisms also exchange energy between the spin subsystems. This spin thermalization may strongly affect thermoelectric properties spin valves, leading, e.g., to violations of the Wiedemann-Franz law.\footnote{Tero T. Heikkil\"a, Moosa Hatami and Gerrit E.W. Bauer, [arXiv:0910.4867].}