Observation of asymmetric distributions of magnetic singularities across magnetic multilayers

Abstract

Whereas a great deal of work is being devoted to magnetic singularities in two-dimensional (2D) systems (surfaces, interfaces, films) due to their possible applications, much less is known about their properties along the perpendicular direction. Here, we report on a pronounced asymmetry of the in-depth distribution of meronlike magnetic textures, which are magnetic singularities similar to ½ skyrmions, in magnetic layers. Meron textures are observed to be distributed in two groups defined by their topology. One of them resides almost exclusively at the top surface of the film and the other at the bottom one. This observation has been brought to light with element-specific magnetic transmission soft x-ray microscopy. Micromagnetic simulations reveal that closure domains are at the origin of this asymmetry. The result might be of general interest for controlling magnetic three-dimensional (3D) architectures.

Topological defects in weak perpendicular magnetic anisotropy NdCo honeycomb lattices

“…MuView code was used for visualization. Material parameters for NdCo nanostructures at room temperature were M S =10 6 A m −1 , A=0.5×10 −11 J m −1 , K N =10 5 J m −3 , as reported before [19]. The lattice was simulated using periodic boundary conditions over space, so that the unit cells are repeated 20×15 times in the longitudinal and transverse directions, respectively.…”

“…These textures present an enhanced topological stability that makes them very suitable for magnetic recording applications and logic devices [10][11][12]. Individual magnetic textures such as artificial skyrmions and merons can also be nucleated via domain imprinting in exchange coupled multilayers playing with geometry, in-plane and out-of-plane anisotropy layers or antiferromagnetic couplings [13][14][15][16][17][18][19]. In the case of magnetic nanostructures with in-plane magnetic anisotropy, magnetic vortices and edge half vortices are the most relevant topological defects needed to understand magnetization reversal [20] in nanowires [21] and bifurcations [22].…”

Stripe domains reorientation in ferromagnetic films with perpendicular magnetic anisotropy

“…Different methods have been pursued for the generation and controlled propagation, including magnetic field, electric current, electric field or mechanical stress [56,59,[62][63][64][65][66]. In some cases, the geometry and local asymmetries of stripe domain patterns have been used to guide the propagation of skyrmions or bubbles [66,67]. Other technological concepts are based on the controlled propagation of spin waves in films and micro/nanostructures through various kinds of spin textures.…”

Deterministic propagation of vortex-antivortex pairs in magnetic trilayers

“…15,16 Stray fields and exchange interactions can be used to imprint complex magnetic textures as bubbles or skyrmions on soft magnetic layers in multilayers combining perpendicular magnetic anisotropy (PMA) and in-plane anisotropy materials. 10,17,18 For example, in NiFe/NdCo(wPMA)/GdCo multilayers, the stripe pattern of the central NdCo layer is replicated at the top NiFe and bottom GdCo layers, 19 including linear defects in the stripe pattern such as dislocations (bifurcations and endpoints). At the onset of in-plane magnetization reversal, magnetic textures such as Q ¼ 1 Bloch points (BP) and Q ¼ 1/2 merons appear in the central NdCo layer and drive the nucleation of reversed nuclei in the permalloy layer.…”

“…At the onset of in-plane magnetization reversal, magnetic textures such as Q ¼ 1 Bloch points (BP) and Q ¼ 1/2 merons appear in the central NdCo layer and drive the nucleation of reversed nuclei in the permalloy layer. 19 Then, the geometry of the stripe pattern and localized asymmetries of the stray field may be used to confine and guide the propagation of these reversed domains in the permalloy layer, without physical patterning.…”