ABSTRACT
The discovery of room-temperature ferromagnetism in van der Waals (vdW) materials opens new avenues for exploring low-dimensional magnetism and its applications in spintronics. Recently, the observation of the room-temperature topological Hall effect in the vdW ferromagnet Fe3GaTe2 suggests the possible existence of room-temperature skyrmions, yet skyrmions have not been directly observed. In this study, real-space imaging was employed to investigate the domain evolution of the labyrinth and skyrmion structure. First, Néel-type skyrmions can be created at room temperature. In addition, the influence of flake thickness and external magnetic field (during field cooling) on both labyrinth domains and the skyrmion lattice is unveiled. Due to the competition between magnetic anisotropy and dipole interactions, the specimen thickness significantly influences the density of skyrmions. These findings demonstrate that Fe3GaTe2 can host room-temperature skyrmions of various sizes, opening up avenues for further study of magnetic topological textures at room temperature.
ABSTRACT
Solomon rings, upholding the symbol of wisdom with profound historical roots, were widely used as decorations in ancient architecture and clothing. However, it was only recently discovered that such topological structures can be formed by self-organization in biological/chemical molecules, liquid crystals, etc. Here, we report the observation of polar Solomon rings in a ferroelectric nanocrystal, which consist of two intertwined vortices and are mathematically equivalent to a [Formula: see text] link in topology. By combining piezoresponse force microscopy observations and phase-field simulations, we demonstrate the reversible switching between polar Solomon rings and vertex textures by an electric field. The two types of topological polar textures exhibit distinct absorption of terahertz infrared waves, which can be exploited in infrared displays with a nanoscale resolution. Our study establishes, both experimentally and computationally, the existence and electrical manipulation of polar Solomon rings, a new form of topological polar structures that may provide a simple way for fast, robust, and high-resolution optoelectronic devices.
ABSTRACT
Antiferroelectric materials have shown potential applications in energy storage. However, controlling and improving the energy-storage performance in antiferroelectric remain challenging. Here, a domain structure and energy-storage performance diagram for Pb(Zr1-xTix)O3 (x ≤ 0.1) single crystal are investigated via phase-field simulations. Controlling the ratio of domain wall coefficients λ and g can tune the periodicities of the antiferroelectric stripe domain and generate a complicated topological domain. By decreasing the antiferroelectric domain periodicity, one can achieve high recoverable energy-storage density (Wrec = 30.24 J/cm3) with an efficiency of 80.9%. In addition, Pb(Zr1-xTix)O3 (x ≤ 0.1) thin-film system has also been investigated. Positive equiaxial misfit strain significantly enhances recoverable energy-storage density up to 21.96 J/cm3 with an efficiency of 84.9%. Our results offer another train of thought to tune antiferroelectric domain structure, which provides the idea to design high-energy-density materials in experiments.
ABSTRACT
In situ electrical control of the Dzyaloshinskii-Moriya interaction (DMI) is one of the central but challenging goals toward skyrmion-based device applications. An atomic design of defective interfaces in spin-orbit-coupled transition-metal oxides can be an appealing strategy to achieve this goal. In this work, by utilizing the distinct formation energies and diffusion barriers of oxygen vacancies at SrRuO3 /SrTiO3 (001), a sharp interface is constructed between oxygen-deficient and stoichiometric SrRuO3 . This interfacial inversion-symmetry breaking leads to a sizable DMI, which can induce skyrmionic magnetic bubbles and the topological Hall effect in a more than 10 unit-cell-thick SrRuO3 . This topological spin texture can be reversibly manipulated through the migration of oxygen vacancies under electric gating. In particular, the topological Hall signal can be deterministically switched ON and OFF. This result implies that the defect-engineered topological spin textures may offer an alternate perspective for future skyrmion-based memristor and synaptic devices.
