Dynamic Phase Diagram of an Orthogonal Spin Torque device: Topological Category

TL;DR

This paper explores the complex nonlinear magnetization dynamics in an orthogonal spin-torque device, presenting a phase diagram that classifies different topological behaviors to aid in designing fast spintronic applications.

Contribution

It introduces a topological classification of dynamic phases in an orthogonal spin-torque device based on a macrospin model, linking phase behavior to device design.

Findings

Rich nonlinear magnetization trajectories identified.

Phase diagram mapped in current density and polarization space.

Topological classification of phases for device optimization.

Abstract

The magnetization evolution of the free layer in an orthogonal spin-torque device is studied based on a macrospin model. The trajectory of magnetization vector under various conditions has shown rich nonlinear properties. The phase diagram is obtained in the parameter spaces of current density and the polarization distribution (the ratio of in-plane and out-of-plane polarizers). These dynamic phases can be classified according to their nonlinear behaviors which are topologically different, namely limit point and/or limit cycle. The topological classification is meaningful to design the ultra-fast spin-torque devices under different dynamic conditions towards various applications such as memory and oscillators.