High frequency operation of a spin‐torque oscillator at low field

Abstract

Abstract We demonstrate a nano‐contact based spin‐torque oscillator (STO) combining a high operating frequency with low field operation. The STO is based on an orthogonal spin‐valve architecture with an in‐plane Co polarizer and an out‐of‐plane Co/Ni multilayer free layer. High frequency operation at low external fields is achieved by tailoring the Co/Ni layer properties to increase the strength ( H k ) of the perpendicular magnetic anisotropy, while simultaneously reducing the saturation magnetization ( M s ). Our approach emphasizes the importance of μ 0 ( H k –M s ) in determining the operating frequency in this system, and suggests that yet higher frequencies should be attainable through further optimization. magnified image (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)