Current-induced bistability and dynamic range of microwave generation in magnetic nanostructures

Abstract

We show analytically that in a current-driven magnetic layered structure there are two critical values of current: ${I}_{\mathrm{min}}$ at which the initially stable minimum of magnetic energy becomes unstable, and ${I}_{\mathrm{max}}$ at which the initially unstable maximum of magnetic energy becomes stable. If ${I}_{\mathrm{min}}<{I}_{\mathrm{max}}$ there is a finite instability interval ${I}_{\mathrm{min}}<I<{I}_{\mathrm{max}}$ where generation of microwave oscillations is possible. If, on the other hand, ${I}_{\mathrm{min}}>{I}_{\mathrm{max}}$, then in the interval ${I}_{\mathrm{min}}>I>{I}_{\mathrm{max}}$ the system demonstrates current-induced bistability, where spontaneous switching takes place between the stable energy minimum and energy maximum stabilized by current.