Microscopic magnetization distribution of Bloch lines in a uniaxial magnet

TL;DR

This study directly observed the microscopic structure of Bloch lines in uniaxial magnets using advanced microscopy, revealing misaligned Bloch walls caused by dipole interactions, which enhances understanding of magnetic microstructures.

Contribution

First direct microscopic observation of Bloch line structures in uniaxial magnets, linking misalignment to dipole interactions through combined microscopy and simulations.

Findings

Edges of Bloch walls are misaligned in Bloch lines.

Misalignment caused by dipole-dipole interactions.

Results improve understanding of nanometer-scale magnetic microstructures.

Abstract

Bloch lines are formed to reduce the magnetostatic energy generated by the Bloch walls in uniaxial magnets. Recently, it is reported that Bloch lines play important roles in the emergence and helicity reversal of magnetic bubbles in Sc-substitute M-type hexaferrites (BaFe$_{12-x-0.05}$Sc$_{x}$Mg$_{0.05}$O$_{19}$). Although Bloch lines have been discussed on the basis of micromagnetic simulations, the detailed structure was not observed directly. In this study, we investigated the microscopic structures of Bloch lines in BaFe$_{10.35}$Sc$_{1.6}$Mg$_{0.05}$O$_{19}$ uniaxial magnets. Differential-phase contrast scanning transmission microscopy (DPC-STEM) directly revealed that the edges of the Bloch walls were misaligned in the Bloch lines of BaFe$_{10.35}$Sc$_{1.6}$Mg$_{0.05}$O$_{19}$. From the micromagnetic simulations based on the Monte-Carlo technique, we showed that the misaligned Bloch walls were caused by the dipole-dipole interactions in the hexaferrite. Our results will help to understand the microstructures of Bloch lines at nanometer scale.