Synthetic Antiferromagnet-Based Spin Josephson Oscillator

Two easy-plane ferromagnetic layers, antiferromagnetically coupled through a thin nonmagnetic metal layer, form the magnetic analog of a Josephson junction. A current driven spin chemical potential drives a 2 pi precession of the in-plane magnetization of each ferromagnet. The participation of the full magnetic moment in the 2 pi precession maximizes the giant magnetoresistance and the ac output power. The frequency can be continuously tuned by a dc bias. An applied ac bias results in a time-averaged magnetoresistance with Shapiro-like steps. The multistate mode-locking behavior exhibited by the Shapiro steps may be exploited for applications such as microwave detectors and neuromorphic computing. They may also serve as an experimental signature of spin superfluidity. Published under license by AIP Publishing.