Controlled nucleation of topological defects in the stripe domain patterns of lateral multilayers with perpendicular magnetic anisotropy

Abstract

Magnetic lateral multilayers have been fabricated on weak perpendicular magnetic anisotropy amorphous Nd-Co films in order to perform a systematic study on the conditions for controlled nucleation of topological defects within their magnetic stripe domain pattern. A lateral thickness modulation of period w is defined on the nanostructured samples that, in turn, induces a lateral modulation of both magnetic stripe domain periods λ and average in-plane magnetization component M in-plane . Depending on lateral multilayer period and in-plane applied field, thin and thick regions switch independently during in-plane magnetization reversal and domain walls are created within the in-plane magnetization configuration coupled to variable angle grain boundaries and disclinations within the magnetic stripe domain patterns. This process is mainly driven by the competition between rotatable anisotropy (that couples the magnetic stripe pattern to in-plane magnetization) and in-plane shape anisotropy induced by the periodic thickness modulation. However, as the structural period w becomes comparable to magnetic stripe period λ, the nucleation of topological defects at the interfaces between thin and thick regions is hindered by a size effect and stripe domains in the different thickness regions become strongly coupled.

Tunable exchange bias-like effect in patterned hard-soft two-dimensional lateral composites with perpendicular magnetic anisotropy

“…In general, the coupling in laterally patterned structures is caused by exchange at the interfaces and magnetostatic charges created by the lateral modulation of in-plane magnetization. 30 In the present case, KM images indicate significant differences in the magnetization reversal of interdisc areas [labeled as I in Fig. 2(d)] and of the linear regions in between the rows of discs [labeled as II in Fig.…”

“…1(d)]. The signal from the disc shows magnetic stripe domains and the etched film around it not, thus we have fabricated an exchange coupled 2D hard-soft system, where the discs present a PMA magnetic material behavior with weak magnetic stripe domains 17,22,30 and the rest of the layer exhibits an in-plane uniaxial magnetization behavior. The magnetic differences between the discs and the etched layer allow us to perform the following experiment to control the magnetization reversal in this last one: first, by the application of an in-plane saturating field (H !…”

“…This shift can be understood in terms of exchange and magnetostatic interactions between the discs and the surrounding etched layer, mainly because of the in-plane magnetization discontinuities at the discs edges. 30 The discs act as nucleation points for the domains in the etched layer with the same orientation than the discs in-plane magnetization (! or ), and because of the stray field generated at the edges, a faster (stronger) growth (pinning) of reversed (original) inter-disc domains takes place.…”

Exchange-Bias Phenomenon: The Role of the Ferromagnetic Spin Structure

“…The latter is an important ingredient which cannot be ignored for the development of EB theories. Moreover, these results imply that complex FM spin textures, as skyrmions or magnetic topological defects [38][39][40] may also show unpredicted dependences when exchange coupled to antiferromagnetic or large anisotropic materials. The active role of the FM spins should also be considered in the design of exchange coupling-based devices or hard/soft heterostructures for ultra-high density storage media.…”

Perpendicular magnetic anisotropy in amorphous NdxCo1−x thin films studied by x-ray magnetic circular dichroism

“…Nowadays, these types of materials still attract great attention since they are used as base materials for the study of novel micro and nanoscopic magnetic phenomena [2][3][4]. The amorphous structure of the magnetic material used in some of these investigations [5][6][7] allows a larger miniaturization, faster preparation process, and more freedom in the choice of the relevant parameters than polycrystalline or monocrystalline materials, especially in the tune of its PMA energy.…”