Role of Magnetic Field in Self-Oscillation of Nanomagnet Excited by Spin Torque

TL;DR

This paper investigates how magnetic field direction influences the critical current and self-oscillation behavior of spin torque oscillators with specific magnetic layer configurations, revealing divergence points and sign changes.

Contribution

It provides new insights into the magnetic field dependence of critical current and oscillation conditions in spin torque oscillators, using analytical solutions of the LLG equation.

Findings

Critical current diverges at certain field directions.

Sign of critical current depends on applied field direction.

Self-oscillation does not occur at divergence points.

Abstract

The critical current of the self-oscillation of spin torque oscillator (STO) consisting of a perpendicularly magnetized free layer and an in-plane magnetized pinned layer was studied by solving the Landau-Lifshitz-Gilbert (LLG) equation. We found that the critical current diverged at certain field directions, indicating that the self-oscillation does not occur at these directions. It was also found that the sign of the critical current changed depending on the applied field direction.