Indication of vortex stabilization and buckling in circular shaped magnetic nanostructures

Abstract

The spin structure and magnetization reversal in Co/Al2O3/Py triple layer nanodots have been investigated both via micromagnetic simulations and experimentally by magneto-optical Kerr effect measurements. Depending on the size, isolated Py dots show either a vortex state or single domain state during magnetization reversal. However, after combining the Py and Co dots in a stack separated by an insulating layer, the reversal process is governed by dipolar coupling between the soft and the hard ferromagnetic layer. Then, by means of micromagnetic simulations, we find either a stabilization and triggering of the vortex state or various types of buckling states. We construct a phase diagram, where regions for either states are marked depending on their respective layer thickness. We have studied two different types of systems with and without preferential anisotropy axis of the Co layer. The experimental results on systems with uniaxial magnetic anisotropy are found to behave as intermediate between these two numerical studies.

Light-Induced Metastable Magnetic Texture Uncovered byin situLorentz Microscopy

“…The spontaneous generation of vortices and antivortices by light in a homogeneous magnetic thin film may at first seem surprising. In localized nanoparticles, vortex structures are typically found as the lowest-energy configuration, stabilized by stray field minimization, [2][3][4][5]36 whereas for homogeneous thin films, as studied here, vortex structures are excited states. Nevertheless, we find the laser-induced vortex-antivortex network to be stable at room temperature, and no relaxation to the equilibrium magnetic ripple structure is observed over a time span of several months.…”

“…Topologically protected magnetic defects cannot be continuously transformed into a defect-free state and therefore may be viewed as quasi-particles, largely robust against thermal perturbation. 1 Depending on the magnetic anisotropy of the structure, magnetic defects of different topology, such as vortices and skyrmions, may exist, often stabilized in tailored nano-structures [2][3][4][5][6] or by intrinsic interactions. 7,8 For the latter case, as a prominent example, the chiral Dzyaloshinskii-Moriya interaction induces ordered Skyrmion lattices in helimagnetic materials, such as MnSi, 9 Fe 1−x Co x Si, 10 or in single-atomic iron layers on an iridium surface.…”