Generation of microwave radiation in planar spin-transfer devices

TL;DR

This paper analyzes how microwave radiation can be generated in planar spin-transfer devices with large easy plane anisotropy, providing analytical insights into switching boundaries and conditions for zero-field oscillations.

Contribution

It introduces a simplified planar model to understand precession states and derives analytical switching boundaries for specific spin-transfer devices.

Findings

Effective planar description explains precession state emergence.

Switching boundaries are analytically derived for collinear and spin-flip devices.

Zero-field microwave oscillations are possible without special torque forms.

Abstract

Current induced precession states in spin-transfer devices are studied in the case of large easy plane anisotropy (present in most experimental setups). It is shown that the effective one-dimensional planar description provides a simple qualitative understanding of the emergence and evolution of such states. Switching boundaries are found analytically for the collinear device and the spin-flip transistor. The latter can generate microwave oscillations at zero external magnetic field without either special functional form of spin-transfer torque, or ``field-like'' terms, if Gilbert constant corresponds to the overdamped planar regime.