Fluctuation model of current-driven magnon excitation

A model is suggested that explains the stationary high-frequency magnetizat ion oscillations observed previously by M. Tsoi et al. when passing dc curr ent through a silver tip mounted on a magnetic Co/Cu multilayer. At the int erface between nonmagnetic and ferromagnetic (N/F) metals, Aronov's gap Del ta (A) (difference in the electrochemical potentials of electrons with oppo site spins) arises upon the passage of electric current, thereby energetica lly promoting magnon creation. Electrons flowing from the nonmagnetic to th e ferromagnetic metal become spin-polarized. In a magnetic field, magnetiza tion fluctuations in a mesoscopic ferromagnet give rise to magnetization pr ecession around the magnetic field. The precession is damped due to the vis cous losses. In the presence of spin-polarized electron flow, the fluctuati ons also produce a current-induced torque that compensates for the dissipat ive torque, leading to stationary high-frequency magnetization oscillations . (C) 2001 MAIK "Nauka/Interperiodica".