Skyrmions in magnetic multilayers

Abstract

Symmetry breaking together with strong spin-orbit interaction give rise to many exciting phenomena within condensed matter physics. A recent example is the existence of chiral spin textures, which are observed in magnetic systems lacking inversion symmetry. These chiral spin textures, including domain walls and magnetic skyrmions, are both fundamentally interesting and technologically promising. For example, they can be driven very efficiently by electrical currents, and exhibit many new physical properties determined by their real-space topological characteristics. Depending on the details of the competing interactions, these spin textures exist in different parameter spaces. However, the governing mechanism underlying their physical behaviors remain essentially the same. In this review article, the fundamental topological physics underlying these chiral spin textures, the key factors for materials optimization, and current developments and future challenges will be discussed. In the end, a few promising directions that will advance the development of skyrmion based spintronics will be highlighted.This review article is organized as follows:1. Topological physics of magnetic skyrmions 1.1 Origin of spin topology 1.2 Real space topological physics 1.3 Topological distinction of bubble-like spin textures 2. Interfacial chiral magnetism 2.1 From spin spiral to chiral domain wall 2.2 Physical origin of the chiral interfacial DMI 2.3 Measurement of the interfacial DMI 2.4 Unique advantages of magnetic skyrmions in heterostructures 3. Current developments in thin-film skyrmions 3.1 Writing and deleting a single skyrmion 3.2 Blowing magnetic skyrmion bubbles 3.3 Moving skyrmions in wires 3.4 Magnetic skyrmions in asymmetric trilayers 3.5 Characteristics of topological trivial bubbles 3.6 Hall effect of topological charge -skyrmion Hall effect 3.7 High frequency dynamics of magnetic skyrmion 3.8 Artificial skyrmions stabilized by interlayer coupling in thin films 3.9 Novel spin-resolved imaging techniques 3.9.1 Lorentz transmission electron microscopy 3.9.2 Spin-polarized low energy electron microscopy 3.9.3 Photoemission electron microscopy 4. PerspectivesRecent advancements in nanotechnology resulted in concomitant progress in magnetism, with two developments being particularly influential in nanomagnetic systems: controlling magnets via electric (field/current) excitations [5][6][7][8] and the discovery of topological spin textures [9]. Electric control of magnetism is made possible by utilizing the coupling between electron spin and its orbital motion.

Enhanced Magnetic Anisotropy and Orbital Symmetry Breaking in Manganite Heterostructures

“…For example, anisotropic magnetism in phase‐separated manganites directly links to magnetic inhomogeneity, where magnetic domains grow along one preferred crystal axis due to the anisotropic free‐energy landscape . In a magnetic system where the spin chirality is allowed, magnetic anisotropy plays a key role in determining the propagation direction of spin spirals and stabilizing subtle spin textures such as skyrmions . For spintronic devices, magnetic anisotropy is required to retrieve the information stored in an antiferromagnet and improves areal density of magnetic memories .…”

A microwave field-driven transistor-like skyrmionic device with the microwave current-assisted skyrmion creation

“…The magnetic skyrmion is an exotic magnetic texture which has a nanoscale vortex-like magnetization structure that is protected by topological invariance [1][2][3][4] . In the recent years, the magnetic skyrmion has been experimentally observed in magnetic materials [5][6][7][8][9][10][11][12][13][14][15][16][17] , semiconductors 18 , multiferroic 19 and ferroelectric 20 materials, which indicates that there are diverse potential applications of magnetic skyrmions in the field of spintronics.…”

Inelastic Spin‐Wave Scattering by Bloch Domain Wall Flexure Oscillations

“…The approach to the SW inelastic scattering used above is based on the interaction of the SWs with the dynamical emergent electromagnetic field generated by the moving inhomogeneous background magnetization texture (in our case, oscillating DW). Such emergent field results, in particular, in the skyrmion/vortex Hall effect and the topological Hall effect detected experimentally in magnetic films and stripes . The non‐linear SW–DW interaction can be also considered as origin of an addition damping of the initial propagating SW ( k , ω k ).…”