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)