Current-Driven Resonances in Magnetic Multilayers

We describe complex variations in resistance of a $\mathrm{C}\mathrm{o}/\mathrm{C}\mathrm{u}$ multilayer, generated by injection of an adjustable dc current density ($\sim {10}^9\mathrm{A}/{\mathrm{c}\mathrm{m}}^2$) via a point contact. We attribute these variations to coupling of current-induced spin waves to lattice vibrations, leading especially to current-driven resonant excitations of phonons. We propose a simple model to explain the observed structured behavior of the variations as a function of the applied current and magnetic field.