Mobility of Bloch Walls via the Collective Coordinate Method

TL;DR

This paper investigates the dissipative motion of Bloch walls in a one-dimensional anisotropic spin chain under magnetic fields, using a collective coordinate approach to analyze mobility, damping, and temperature effects.

Contribution

It introduces an effective Hamiltonian for Bloch walls coupled to magnetic excitations, providing new insights into their mobility and damping under external fields and temperature.

Findings

Wall mobility remains finite at finite external fields.

The spectrum of the potential varies with magnetic field strength.

Damping constant depends on temperature and magnetic field.

Abstract

We have studied the problem of the dissipative motion of Bloch walls considering a totally anisotropic one dimensional spin chain in the presence of a magnetic field. Using the so-called "collective coordinate method" we construct an effective Hamiltonian for the Bloch wall coupled to the magnetic excitations of the system. It allows us to analyze the Brownian motion of the wall in terms of the reflection coefficient of the effective potential felt by the excitations due to the existence of the wall. We find that for finite values of the external field the wall mobility is also finite. The spectrum of the potential at large fields is investigated and the dependence of the damping constant on temperature is evaluated. As a result we find the temperature and magnetic field dependence of the wall mobility.