Continuous Neel to Bloch Transition as Thickness Increases: Statics and Dynamics

TL;DR

This paper investigates the transition from Neel to Bloch domain walls in magnetic films as thickness increases, analyzing static and dynamic properties including a second order phase transition.

Contribution

It provides a detailed analysis of the Neel to Bloch transition, identifying the critical mode and its behavior, supported by analytical Landau theory and numerical results.

Findings

The transition is second order at a critical thickness hc.

A single unstable mode mediates the transition, with oscillatory motion.

The critical mode frequency scales as the square root of (hc - h).

Abstract

We analyze the properties of Neel and Bloch domain walls as a function of film thickness h, for systems where, in addition to exchange, the dipole-dipole interaction must be included. The Neel to Bloch phase transition is found to be a second order transition at hc, mediated by a single unstable mode that corresponds to oscillatory motion of the domain wall center. A uniform out-of-plane rf-field couples strongly to this critical mode only in the Neel phase. An analytical Landau theory shows that the critical mode frequency varies as the square root of (hc - h) just below the transition, as found numerically.