Coarsening dynamics of topological defects in thin permalloy films

Abstract

We study the dynamics of topological defects in the magnetic texture of rectangular permalloy thin-film elements during relaxation from random magnetization initial states. Our full micromagnetic simulations reveal complex defect dynamics during relaxation towards the stable Landau closure domain pattern, manifested as temporal power-law decay, with a system-size-dependent cutoff time, of various quantities. These include the energy density of the system and the number densities of the different kinds of topological defects present in the system. The related power-law exponents assume nontrivial values and are found to be different for the different defect types. The exponents are robust against a moderate increase in the Gilbert damping constant and introduction of quenched structural disorder. We discuss details of the processes allowed by conservation of the winding number of the defects, underlying their complex coarsening dynamics.

The effect of edge-roughness of magnetic nanowires on the degree of asymmetry in transverse domain walls

“…Understanding the effect of experimental parameters on the characteristics of domain walls in magnetic nanowires is important for the success of their promising applications for emerging spin electronics, including racetrack memory devices, 1 magnetic logic gates, 2 and other low-dimensional applications. [1][2][3][4][5] A greater understanding of the fabrication process can provide a deep insight into the fundamental properties of the materials, such as microstructural properties, [6][7][8][9] domain wall (DW) dynamics, [10][11][12][13] and correlations between structural defects and electronic/magnetic properties. 12,13 When the width and thickness of a nanowire are scaled down to the nanoscale, a number of features will change.…”

Field-driven single domain wall motion in ferromagnetic nanowires

“…A TDW can be transformed to a VDW during the propagation process, due to defects, constrictions or protrusions. 17,[24][25][26][27][28][29][30] The CCW-VDW intentionally created at the C 1 area in the nucleation process of the simulation, whilst the chirality of the created DW in the experiment largely depends on the nucleation eld orientation and topological spin congurations at the C 1 . 27,34 Field-driven single DW motion in the given DWT structures was investigated by means of OOMMF simulation and Lorentz microscopy studies.…”

“…To create a single DW instead of using an external eld applies with the angle a in respect of the direction vertical to the easy axis of the DWT structure, 11,14 scientists from various research groups have investigated DWT nanostructures with restrictions or protrusions, [15][16][17][18][19][20] at which an injection pad was attached to one end of these structures. Such structures can provide a single H2H DW, created at the junction between the injection pad and the remaining part of the structure.…”

Edge defects inducing asymmetric transverse domain walls created in Ni80Fe20 nanowires

“…The principle of OOMMF simulations is based on the Landau-Lifshitz-Gilbert equation for the precession and damping of the magnetization (M) under an external magnetic field (H e ) [4,17,22,23].…”