High Q factor over 3000 due to out-of-plane precession in nano-contact spin-torque oscillator based on magnetic tunnel junctions

We investigated microwave oscillation in a sombrero-shaped nano-contact spin-torque oscillator under an external magnetic field with an out-of-plane component. By increasing the out-of-plane field, we observed an abrupt change from in-plane precession to out-of-plane precession around the effective demagnetization field of the free layer. The out-of-plane precession under optimized conditions yielded not only a fundamental oscillation peak with a very large Q factor (3200) but also higher-order harmonic peaks with frequencies up to at least 45 GHz. A high Q factor and high-frequency oscillations are of great importance for device applications such as telecommunications, radar sensors, and high-speed magnetic field sensors.