The dynamics of magnetic vortex states in a single permalloy nanoparticle

TL;DR

This study introduces a new electron transport measurement technique to observe magnetic vortex state dynamics in single permalloy nanoparticles, revealing vortex resonance frequencies and widths at room temperature.

Contribution

It presents a novel method for studying magnetic vortex dynamics in individual nanoparticles using magnetotransport measurements with RF fields.

Findings

Vortex core resonance frequencies identified.

Resonance widths estimated below 6 MHz.

Magnetic vortex states influence resistance and DC voltage levels.

Abstract

We demonstrate a novel method allowing the study of the magnetic state dynamics of a single nanoparticle by means of electron transport measurements. Elliptical 550 nm x 240 nm permalloy nanoparticles are wired with non-magnetic leads for magnetotransport measurements in the presence of a radio-frequency (RF) field. Their resistance exhibits sharp jumps due to the anisotropic magnetoresistance even at room temperature. An RF field induces DC voltage across the nanoparticle which can be partially depleted at a certain RF frequency when a magnetic vortex core resonance is present. An application of an additional DC magnetic field eliminates the vortex and reinstates the unperturbed DC voltage level. The vortex core resonance frequencies are found and the smallest resonance widths are estimated to be less than 6 MHz.