The analysis of two-dimensional domain wall structures by Lorentz microscopy

Abstract

The technique for the study of the inhomogeneous magnetisation components of domain walls by Lorentz microscopy [15] is extended to cover structures which are not stray‐field‐free. Permitted forms for the distributions of the inhomogeneous components are derived and variants of the forms of vortex structures are considered. Results are presented of the application of the technique to 90° and 180° walls in (001) nickel platelets with thicknesses in the range 530 to 4230 Å. Below the critical thickness for stripe domain nucleation (≈︁2800 Å), 90° walls exhibit a pure Néel structure, as do 180° walls in thicknesses up to about 1000 Å. In the thickness range 1000 to 2800 Å 180° walls conform closely to the predicted vortex structure [11, 12]. These 180° walls are found to be subdivided through changes in the vortex corresponding to the predicted variants. Structures are proposed for the junctions in the subdivided walls, one of which may contain a Bloch point. At thicknesses greater than approximately 2800 Å, stripe domains are found to seriously modify the wall structures.

<I>In Situ</I> Lorentz Microscopy Observation of Displaced Chain Walls in Permalloy

“…The simplest way to study technical magnetization process in TEM is to use a perpendicular magnetic field produced by the objective lens itself. 15,16) When the standard objective lens is excited slightly, the resulting in-plane component of the magnetic field can be used for magnetizing experiments by tilting the specimen. However, more direct observations without tilting can be performed if the magnetic field is generated by magnetizing coils 17,18) or a new design of ''magnetizing stage'' [19][20][21] (i.e.…”

Transition micromagnetic structures in asymmetric vortexlike domain walls (Static solutions and dynamic reconstructions)

“…As follows from experimental works, various types of TMSs exist (see, e.g., [9,10,32]). In particular, some fragments of the images of the surface magneti zation distributions obtained in [32] with high resolu tion Kerr microscopy are likely to correspond to TMSs of types A, B, and C (i.e., structures T3, T1, and T2 in terms of [32]).…”

“…Only as a result of long term efforts, it was found (theoretically [7] and experimentally [8]) that the structure of walls in such films has a two dimensional asymmetric M distribution. When ana lyzing the experimental data from [9,10], the authors of [9] concluded that three types of TMSs that sepa rate regions of asymmetric domain walls with different structures (with the location of vortices on the left or right of the central line of a wall, with the clock or counterclockwise rotation of magnetization in vorti ces) can exist. Three dimensional numerical simula tion, which was first performed in [11][12][13][14], supported the two dimensionality and asymmetry of the walls and showed that TMSs that separate regions in asym metric walls are substantially three dimensional local objects.…”

“…TMSs can be both single SPs and combined MSs (clusters) containing several SPs and VBLs. The assumption of the presence of SP in the TMSs of the type under study was made in [10]; however, solutions with SPs were not found in [11][12][13][14].…”

Simulation of three-dimensional micromagnetic structures in magnetically uniaxial films with in-plane anisotropy. Dynamics and structural reconstructions

“…The experimental investigations [2,3] have shown the existence of three types of transition micromagnetic structures (TMSs), which connect regions of various types of vortex walls. It follows from the results of 3D simulation [4][5][6][7][8] that these TMSs have a complex structure including, in particular, the vortices and antivortices on the film surfaces [4][5][6][7] and singular points (SPs) [8].…”