Frequency domain studies of current-induced magnetization dynamics in single magnetic-layer nanopillars

TL;DR

This study investigates high-frequency magnetization dynamics in single cobalt-layer nanopillars induced by spin transfer torque, revealing vortex-core and spin-wave modes with high coherence, consistent with theoretical models.

Contribution

It provides direct experimental evidence of two distinct precessional modes in nanopillars, confirming recent theoretical predictions and demonstrating high coherence of magnetic excitations.

Findings

Identification of vortex-core and spin-wave precessional modes

High coherence with a linewidth of 4 MHz at room temperature

Mode excitation depends on magnetic field and current polarity

Abstract

Spin transfer torque-induced high-frequency dynamics of single thin cobalt-layer nanopillars of circular and elliptical shape have been observed directly. Two types of precessional modes can be identified as a function of magnetic field perpendicular to the layer plane, excited for negative current polarity only. They are assigned to vortex-core and transverse spin-wave excitations, which corroborate recent model predictions. The observed narrow linewidth of 4 MHz at room temperature indicates the high coherence of the magnetic excitations.