Thermally Assisted Current-Driven Bistable Precessional Regimes in Asymmetric Spin Valves

TL;DR

This paper investigates thermally assisted current-driven precessional regimes in asymmetric spin valves, revealing bistability, thermally induced transitions, and their impact on oscillation frequency and power spectrum.

Contribution

It introduces the discovery of a bistable precessional regime in asymmetric spin valves and analyzes thermal effects on oscillation dynamics.

Findings

Bistable precessional regimes exist in asymmetric spin valves.

Thermal fluctuations induce transitions between oscillatory states.

Power spectrum is dominated by out-of-plane oscillations in the bistable region.

Abstract

Spin-transfer torque in asymmetric spin valves can destabilize both parallel and antiparallel configurations and can lead to precessional modes also in the absence of an external magnetic field. We find a bistable precessional regime in such systems and show that thermal fluctuations can excite transitions (telegraph noise) between the corresponding oscillatory regimes that are well separated by irreversible paths at low temperatures. Because of the thermally induced transitions, the frequency of the resulting current-driven oscillations is different from that obtained at very low temperatures. We also show that the power spectrum in the bistable region is dominated by the out-of-plane oscillatory mode.