Externally-driven transformations of vortex textures in flat submicrometer magnets
arXiv:1205.5008 · doi:10.1103/PhysRevB.85.184421
Abstract
Two effects of oscillatory transformations of vortex textures in flat nanomagnets due to the application of an external field or a spin-polarized electric current are analytically described with relevance to soft-magnetic structures of submicrometer sizes (whose thickness is significantly bigger than the magnetostatic exchange length). These are changes of a domain wall (DW) structure in a long magnetic stripe (oscillations between a transverse DW, a vortex DW, and an antivortex DW) and periodic vortex-core reversals in a circular magnetic dot which are accompanied by oscillatory displacements of the vortex from the dot center. In nanostructures of smaller thicknesses (comparable to the exchange length), where nonlocal magnetostatic effects are very strong because of fast spatial variation of the magnetization, similar phenomena have been widely studied previously. Here, the dynamics is investigated within a local approach including magnetostatic field via boundary conditions on solutions to the Landau-Lifshitz-Gilbert equation only. Both the DWs in stripes and vortex states of the dot are treated as fragments of a cross-tie DW. Despite similarity of the cyclic transformations of the ordering to the dynamics of more strongly confined nanomagnets, details of motion (trajectories) of the vortices and antivortices (Bloch lines) of the textures under study are different, which is related to prohibition of rapid jumps of the polarization of Bloch lines. In addition to the magnetization rotation about the direction of magnetic field or current polarization, the evolution of textures is shown to relate to oscillatory changes of the direction of a cross-tie DW with respect to any arbitrary axis in the magnet plane accompanied by oscillations of the DW width.
References in corpus (22)
- Microwave Oscillations of a Nanomagnet Driven by a Spin-Polarized Current
- Micromagnetic understanding of current-driven domain wall motion in patterned nanowires
- Magnetic vortex oscillator driven by dc spin-polarized current
- Dynamics of domain walls in magnetic nanostrips
- Fractional vortices and composite domain walls in flat nanomagnets
- Spin-Torque Driven Magnetization Dynamics: Micromagnetic Modelling
- Stability of magnetic vortex in soft magnetic nano-sized circular cylinder
- Vortices in thin ferromagnetic films and the skyrmion number
- Vortex oscillations induced by a spin-polarized current in a magnetic nanopillar: Evidence for a failure of the Thiele approach
- Understanding of complex periodic transformations of moving domain walls in magnetic nanostripes
- Dynamics of a vortex domain wall in a magnetic nanostrip: an application of the collective coordinate approach
- Excitation of spin dynamics by spin-polarized current in vortex state disks
- Magnetization Switching in Nanowires: Monte Carlo Study with Fast Fourier Transformation for Dipolar Fields
- Effects of Disorder and Internal Dynamics on Vortex Wall Propagation
- Current-induced vortex displacement and annihilation in a single Permalloy disk
- Magnetization patterns in ferromagnetic nano-elements as functions of complex variable
- Quantitative understanding of magnetic vortex oscillations driven by spin-polarized out-of-plane dc current: Analytical and micromagnetic numerical study
- Non-linear vortex dynamics and transient effects in ferromagnetic disks
- A simple analytical description for the cross-tie domain wall structure
- Spin-Transfer Torque Induced Vortex Dynamics in Fe/Ag/Fe Nanopillars
- Effective anisotropy of thin nanomagnets: beyond the surface anisotropy approach
- Externally-driven transmission and collisions of domain walls in ferromagnetic wires