Magnetization transport across a ferromagnetic-paramagnetic interface

The transport of magnetization across a metallic ferromagnetic-paramagnetic bilayer is investigated using electron spin resonance. The ferromagnetic resonance and transmission electron spin resonance of films of palladium-iron alloys (${\mathrm{Pd}}_{100\mathrm{-}\mathrm{x}}$ ${\mathrm{Fe}}_{\mathrm{x}}$, 0.5≲x≲4) on copper foils are measured. The data are analyzed using a phenomenological model with two proposed mechanisms to couple the magnetizations in the film and the copper. One mechanism is the diffusion of electrons across the interface; the other is an exchange torque across the interface. The dominant coupling mechanism is found to be diffusion of electrons. The model, in addition, accounts well for the angular variation of the spin resonance signal at a fixed temperature. Finally it describes moderately well the variations with temperature of the spin resonance signal over the temperature range in which the magnetization and ferromagnetic resonance linewidth of the ferromagnetic film are varying dramatically.