Spin-torque-driven parametric resonance

PAPER: C. Wang, H. Seinige, and M. Tsoi,

“Current-driven parametric resonance in magnetic multilayers”,

J. Phys. D: Appl. Phys. 46, 285001 (2013).

SLIDES: SPIE Optics+Photonics 2013, Spintronics VI, San Diego, 2013

San Diego, August 27, 2013

ABSTRACT:

Current-induced parametric excitations were observed in point-contact spin-valve nanodevices. Point contacts were used to inject high densities of direct and microwave

currents into spin valves, thus producing oscillating spin-transfer and Oersted-field torques on magnetic moments. The resulting magnetodynamics were observed electrically by measuring rectified voltage signals across the contact. In addition to the spin-torque-driven ferromagnetic resonance we observe doubled-frequency signals which correspond to the parametric excitation of magnetic moments. Numerical simulations suggest that both ac spin-torque and ac Oersted field contribute to the parametrically excited dynamics while dc spin-torque can switch it on and off. The dc bias dependence of the parametric resonance signal enabled the mapping of instability regions characterizing the nonlinearity of the oscillation.

This work was supported in part by NSF Grants DMR-0645377 and DMR-1207577