Spin-Wave Excitations in Nanopillars With Perpendicular Polarizers

Spin-transfer-induced spin-wave excitations in spin-valve nanopillars with perpendicular polarizers have been investigated by micromagnetic simulations. Two coexistent steady states with in-plane magnetizations are observed at small current. With the increased current, periodic oscillating spin waves with frequency from several to tens of gigahertz can be tuned by current alone. High-order harmonics with odd times of fundamental frequency only are observed in these periodic oscillations. The fundamental frequency decreases with the increased thickness of the free layer. Large current could excite chaotic spin waves