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.

Contacting ferromagnetic films with normal metals changes how magnetic textures respond to electric currents, enabling surprisingly fast domain wall motions and spin texture-dependent propagation direction. These effects are attributed to domain wall chirality induced by the Dzyaloshinskii-Moriya interaction at interfaces, which suggests rich possibilities to influence domain wall dynamics if the Dzyaloshinskii-Moriya interaction can be adjusted. Chiral magnetism was seen in several film structures on appropriately chosen substrates where interfacial spin-orbit-coupling effects are strong. Here we use real-space imaging to visualize chiral domain walls in cobalt/nickel multilayers in contact with platinum and iridium. We show that the Dzyaloshinskii-Moriya interaction can be adjusted to stabilize either lefthanded or right-handed Néel walls, or non-chiral Bloch walls by adjusting an interfacial spacer layer between the multilayers and the substrate. Our findings introduce domain wall chirality as a new degree of freedom, which may open up new opportunities for spintronics device designs.

Lithium dendrite (filament) propagation through ceramic electrolytes, leading to short-circuits at high rates of charge, is one of the greatest barriers to realising high energy density all-solidstate lithium anode batteries. Utilising in-situ X-ray computed tomography coupled with spatially mapped X-ray diffraction, the propagation of cracks and the propagation of lithium dendrites through the solid electrolyte have been tracked in a Li/Li6PS5Cl/Li cell as a function of the charge passed. On plating, cracking initiates with spallation, conical "pothole"-like cracks that form in the ceramic electrolyte near the surface with the plated electrode. The spallations form predominantly at the lithium electrode edges where local fields are high. Transverse cracks then propagate from the spallations across the electrolyte from the plated to the stripped electrode. Lithium ingress drives the propagation of the spallation and transverse cracks by widening the crack from the rear, i.e. the crack front propagates ahead of the Li. As a result, cracks traverse the entire electrolyte before the Li arrives at the other electrode and therefore before a short-circuit occurs.

The possibility of utilizing the rich spin-dependent properties of graphene has attracted much attention in the pursuit of spintronics advances. The promise of high-speed and low-energy-consumption devices motivates the search for layered structures that stabilize chiral spin textures such as topologically protected skyrmions. Here we demonstrate that chiral spin textures are induced at graphene/ferromagnetic metal interfaces. Graphene is a weak spin-orbit coupling material and is generally not expected to induce a sufficient Dzyaloshinskii-Moriya interaction to affect magnetic chirality. We demonstrate that indeed graphene does induce a type of Dzyaloshinskii-Moriya interaction due to the Rashba effect. First-principles calculations and experiments using spin-polarized electron microscopy show that this graphene-induced Dzyaloshinskii-Moriya interaction can have a similar magnitude to that at interfaces with heavy metals. This work paves a path towards two-dimensional-material-based spin-orbitronics.