Abstract
Using nonlinear system theory and numerical simulations, we map out the static and dynamic phase diagrams in the zero applied field of a spin torque nano device with a tilted polarizer (TP). We find that for sufficiently large currents, even very small tilt angles (β>1°) will lead to steady free layer precession in zero field. Within a rather large range of tilt angles, 1°<β<19°, we find coexisting static states and hysteretic switching between these using only current. In a more narrow window (1°<β<5°) one of the static states turns into a limit cycle (precession). The coexistence of current-driven static and dynamic states in the zero magnetic field is unique to the TP device and leads to large hysteresis in the upper and lower threshold currents for its operation. The nano device with TP can facilitate the generation of large amplitude mode of spin torque signals without the need for cumbersome magnetic field sources and thus should be very important for future telecommunication applications based on spin transfer torque effects.
Highlights
Using non-linear system theory and numerical simulations we map out the static and dynamic phase diagram in zero applied field of a spin torque oscillator with a tilted polarizer (TP-spin torque oscillators (STO))
In this Letter, we study the static and dynamic phase diagram of a spin valve where the magnetization of the fixed layer is tilted at an arbitrary angle out of the film plane
The coexistence of static and dynamic states in zero field is unique to the Tilted Polarizer STO (TP-STO) and disappears for polarizer angles outside of 1◦ < β < 19◦
Summary
Using non-linear system theory and numerical simulations we map out the static and dynamic phase diagram in zero applied field of a spin torque oscillator with a tilted polarizer (TP-STO). In this Letter, we study the static and dynamic phase diagram of a spin valve where the magnetization of the fixed layer is tilted at an arbitrary angle out of the film plane. We here show, using non-linear system analysis, that the deviation from in-plane orientation creates a surprisingly rich phase diagram with coexistence of different static and dynamic states within a certain range of the polarizer tilt angle β.
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