Magnetodynamics in orthogonal nanocontact spin-torque nano-oscillators based on magnetic tunnel junctions

We demonstrate the magnetodynamics of nanocontact spin-torque nano-oscillators based on magnetic tunnel junctions, with a strong perpendicular magnetic anisotropy free layer and an easy-plane reference layer. First, the static magnetic properties are studied by conducting hysteresis loop and magnetoresistance measurements. Then, we characterize the generated microwave signals by applying dc currents. Field-sweep signals at xed current show a typical FMR-like frequency dependence. Interestingly, for current-sweep measurements, the plot of frequency versus dc current can be fitted well with a symmetric parabolic and an asymmetric linear term. The symmetric behavior is ascribed to the current-induced Joule heating and Oersted elds. The asymmetric dependence is due to the linear perpendicular spin torque (or eld-like torque) and the voltage-controlled magnetic anisotropy. Our observation hints at a route to improving the frequency tunability in future spintronic applications by selectively adding all these contributions.
QC 20180907