Spin-dependent thermal transport perpendicular to the planes of Co/Cu multilayers

We report measurements of the cross-plane thermal conductivity of periodic Co/Cu multilayers using time-domain thermoreflectance. The cross-plane thermal conductivity increases from ~18 W0.16em0exm^-10.16em0exK^-1 at remanence to ~32 W0.16em0exm^-10.16em0exK^-1 at saturation fields. This giant magnetothermal resistance (GMTR) effect is consistent with predictions based on the Wiedemann-Franz law. We discuss the role of a spin-dependent temperature, known as spin heat accumulation, in GMTR experiments and develop a three-temperature model capable of predicting the time evolution of the temperatures of majority-spin electrons, minority-spin electrons, and phonons subsequent to pulsed laser heating.