Bloch lines in thin films with perpendicular magnetic anisotropy and intermediate quality factor

I M Izmozherov,V V Zverev,Erlan Zh Baykenov

doi:10.1088/1742-6596/1389/1/012002

I M Izmozherov, V V Zverev + Show 1 more

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https://doi.org/10.1088/1742-6596/1389/1/012002

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Abstract

Bloch lines (BLs) are linear topological defects of magnetic domain walls structure, studied well for bubble domain materials. We investigate its structure and role in magnetization reversal for thin ferromagnetic films with perpendicular magnetic anisotropy and intermediate quality factor. We observe vertical BLs with Bloch points and U-shaped structures with vertical and horizontal parts in three-dimensional micromagnetic simulations for Q = 0.34. Also we suggest analytical model functions, describing 3D magnetization distribution in domain walls with BLs.

Highlights

The domain structure (DS) of ferromagnetic thin films impacts significantly on macroscopic properties
We suggest a 3D model distribution describing the magnetization in Bloch lines (BLs), containing Bloch points (BPs), and prove its consistency by direct comparison with the distributions obtained in simulations, as well as calculating the the skyrmion number
Description of a function We present here an analytical model, describing three-dimensional structure of the Bloch line in material with intermediate quality factor 0.1 < Q < 1

Summary

Introduction

The domain structure (DS) of ferromagnetic thin films impacts significantly on macroscopic properties (hysteresis, magnetostriction, etc.). Structural elements with non-trivial topological charge can be observed on domain walls (DWs) They are classified as linear and point defects (solitons) of magnetization vector field: Bloch lines (BLs) and Bloch points (BPs). 1389 (2019) 012002 doi:10.1088/1742-6596/1389/1/012002 has opposite reversal directions Due to these reasons BLs are not strictly vertical. They do not reach film surfaces, being itself the part of Neel DW, and consist of two fragments, with opposite chirality, separated by a BP. These BL structures have been observed in micromagnetic simulations in the DS in a 200 nm thick film with Co (0001) material parameters [4]. To exclude misunderstanding in chapters we always will use term ”simulations” speaking about micromagnetics, and ”model” speaking about analytical distribution

Problem definition

Conclusions