Macroscopic Quantum Tunneling of Ferromagnetic Domain Walls

TL;DR

This paper investigates quantum tunneling of ferromagnetic domain walls, providing improved models for the tunneling process, and calculates the crossover temperatures and tunneling rates for different materials and geometries.

Contribution

It introduces refined expressions for domain wall mass and pinning potential, leading to different predictions for quantum tunneling behavior in ferromagnetic materials.

Findings

Crossover temperatures around 5 mK for Ni and YIG.

WKB exponent is two orders of magnitude larger than previous estimates.

Provides estimates for the transition from 3D to 1D magnetic behavior.

Abstract

Quantum tunneling of domain walls out of an impurity potential in a mesoscopic ferromagnetic sample is investigated. Using improved expressions for the domain wall mass and for the pinning potential, we find that the cross-over temperature between thermal activation and quantum tunneling is of a different functional form than found previously. In materials like Ni or YIG, the crossover temperatures are around 5 mK. We also find that the WKB exponent is typically two orders of magnitude larger than current estimates. The sources for these discrepancies are discussed, and precise estimates for the transition from three-dimensional to one-dimensional magnetic behavior of a wire are given. The cross-over temperatures from thermal to quantum transitions and tunneling rates are calculated for various materials and sample sizes.