Zero-field precession and hysteretic threshold currents in a spin torque nano device with tilted polarizer

Abstract

Using non-linear system theory and numerical simulations we map out the\nstatic and dynamic phase diagram in zero applied field of a spin torque\noscillator with a tilted polarizer (TP-STO).We find that for sufficiently large\ncurrents, even very small tilt angles (beta>1 degree) will lead to steady free\nlayer precession in zero field. Within a rather large range of tilt angles, 1\ndegree< beta <19 degree, we find coexisting static states and hysteretic\nswitching between these using only current. In a more narrow window (1\ndegree<beta<5 degree) one of the static states turns into a limit cycle\n(precession). The coexistence of static and dynamic states in zero magnetic\nfield is unique to the tilted polarizer and leads to large hysteresis in the\nupper and lower threshold currents for TP-STO operation.\n