Magnetic vortex echoes: application to the study of arrays of magnetic nanostructures

TL;DR

This paper introduces a method to generate and analyze magnetic echoes in nanomagnet arrays using vortex core gyrotropic motion, enabling the study of inhomogeneity and interactions through micromagnetic simulations.

Contribution

It presents a novel magnetic echo technique based on vortex core dynamics in nanostructures, with demonstrated applications in measuring inhomogeneity and magnetic interactions.

Findings

Magnetic echoes can be generated in nanomagnet arrays using vortex core inversion.

The relaxation times depend on inhomogeneity, interactions, and damping.

The method reveals a power-law dependence of interaction strength on nanodisk separation.

Abstract

We propose the use of the gyrotropic motion of vortex cores in nanomagnets to produce a magnetic echo, analogous to the spin echo in NMR. This echo occurs when an array of nanomagnets, e.g., nanodisks, is magnetized with an in-plane (xy) field, and after a time \tau a field pulse inverts the core magnetization; the echo is a peak in M_{xy} at t=2\tau. Its relaxation times depend on the inhomogeneity, on the interaction between the nanodots and on the Gilbert damping constant \alpha. Its feasibility is demonstrated using micromagnetic simulation. To illustrate an application of the echoes, we have determined the inhomogeneity and measured the magnetic interaction in an array of nanodisks separated by a distance d, finding a d^{-n} dependence, with n\approx 4.