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

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 (Hk) of the perpendicular magnetic anisotropy, while simultaneously reducing the saturation magnetization (Ms). Our approach emphasizes the importance of μ0(Hk-Ms) in determining the operating frequency in this system, and suggests that yet higher frequencies should be attainable through further optimization. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) In this Letter the authors demonstrate a nanocontact spin-torque oscillator (STO) 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 of the perpendicular magnetic anisotropy, while simultaneously reducing the saturation magnetization. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.