Stochastic resonance of a nanomagnet excited by spin transfer torque

TL;DR

This paper reports the observation of thermally activated stochastic resonance in nanomagnets driven by spin transfer torque, revealing how temperature enhances nonlinear magnetization dynamics and enabling potential applications in nanoscale microwave detection.

Contribution

It introduces the concept of non-adiabatic stochastic resonance in nanomagnets driven by spin transfer torque, highlighting the role of thermal fluctuations in nonlinear dynamics.

Findings

Temperature amplifies GHz precession amplitude.

Weak alternating spin transfer torque can excite nonlinear states.

Thermally activated stochastic resonance observed in nanomagnets.

Abstract

Spin transfer torque from spin-polarized electrical current can excite large-amplitude magnetization dynamics in metallic ferromagnets of nanoscale dimensions. Since magnetic anisotropy energies of nanomagnets are comparable to the thermal energy scale, temperature can have a profound effect on the dynamics of a nanomagnet driven by spin transfer torque. Here we report the observation of unusual types of microwave-frequency nonlinear magnetization dynamics co-excited by alternating spin transfer torque and thermal fluctuations. In these dynamics, temperature amplifies the amplitude of GHz-range precession of magnetization and enables excitation of highly nonlinear dynamical states of magnetization by weak alternating spin transfer torque. We explain these thermally activated dynamics in terms of non-adiabatic stochastic resonance of magnetization driven by spin transfer torque. This type of magnetic stochastic resonance may find use in sensitive nanometer-scale microwave signal detectors.