Magnetic field angle dependence of out-of-plane precession in spin torque oscillators having an in-plane magnetized free layer and a perpendicularly magnetized reference layer

Abstract

Out-of-plane (OP) precession in spin torque oscillators having an in-plane (IP) magnetized free layer and a perpendicularly magnetized reference layer was studied. The bias voltage (VB) and magnetic field angle (θ) dependence of the OP precession were investigated. The absolute values of the critical magnetic fields ( and ) between which OP precession is excited increased as VB increased and as θ changed from the IP to the OP direction. The IP components of converged to a constant value regardless of θ. This result indicates that excitation of OP precession is suppressed entirely by the IP component of the magnetic field, and the contribution of the OP component can be ignored. The experimentally observed precession behavior was successfully modeled by macrospin simulations.