Spin Torque Oscillations Triggered by In-plane Field

TL;DR

This study investigates spin torque nano oscillators, demonstrating that short in-plane magnetic field pulses can trigger and tune high-frequency self-oscillations, with stability confirmed against thermal noise.

Contribution

It reveals that short in-plane magnetic fields can initiate and control high-frequency oscillations in spin torque nano oscillators, and quantifies the effects of field-like torque and thermal noise.

Findings

Oscillations triggered by short in-plane magnetic field pulses.

Oscillation frequency tunable from ~25 GHz to ~72 GHz by current.

Field-like torque increases frequency by up to 10 GHz.

Abstract

We study the dynamics of a spin torque nano oscillator that consists of parallelly magnetized free and pinned layers by numerically solving the associated Landau-Lifshitz-Gilbert-Slonczewski equation in the presence of a field-like torque. We observe that an in-plane magnetic field which is applied for a short interval of time ($<$1ns) triggers the magnetization to exhibit self-oscillations from low energy initial magnetization state. Also, we confirm that the frequency of oscillations can be tuned over the range $\sim$25 GHz to $\sim$72 GHz by current, even in the absence of field-like torque. We find the frequency enhancement up to 10 GHz by the presence of field-like torque. We determine the Q-factor for different frequencies and show that it increases with frequency. Our analysis with thermal noise confirms that the system is stable against thermal noise and the dynamics is not altered appreciably by it.