Quantum depinning of the magnetic vortex core in micron-size permalloy disks

TL;DR

This paper presents experimental evidence of quantum tunneling of the vortex core in micron-sized permalloy disks, revealing quantum dynamics induced by in-plane magnetic fields and associated with structural defects.

Contribution

It is the first to demonstrate quantum tunneling of vortex cores in micron-scale ferromagnetic disks through experimental observation.

Findings

Quantum tunneling of vortex core observed

Vortex dynamics influenced by structural defects

Experimental evidence of quantum effects in nanomagnetism

Abstract

The vortex state, characterized by an in-plane closed flux domain structure and an out-of-plane magnetization at its centre (the vortex core), is one of the magnetic equilibria of thin soft ferromagnetic micron-size dots. In the last two decades many groups have been working on the dynamics of the magnetic moment in nanomagnetic materials at low temperatures, it giving rise to the observation of quantum relaxations and quantum hysteresis cycles. For the first time, we report experimental evidence of quantum dynamics of the vortex core of micron-size permalloy (Fe$_{19}$Ni$_{81}$) disks induced by the application of an in-plane magnetic field. It is attributed to the quantum tunneling of the vortex core through pinning barriers, which are associated to structural defects in the dots, towards its equilibrium position.