Skyrmion phase and competing magnetic orders on a breathing kagomé lattice

Abstract

Magnetic skyrmion textures are realized mainly in non-centrosymmetric, e.g. chiral or polar, magnets. Extending the field to centrosymmetric bulk materials is a rewarding challenge, where the released helicity/vorticity degree of freedom and higher skyrmion density result in intriguing new properties and enhanced functionality. We report here on the experimental observation of a skyrmion lattice (SkL) phase with large topological Hall effect and an incommensurate helical pitch as small as 2.8 nm in metallic Gd3Ru4Al12, which materializes a breathing kagomé lattice of Gadolinium moments. The magnetic structure of several ordered phases, including the SkL, is determined by resonant x-ray diffraction as well as small angle neutron scattering. The SkL and helical phases are also observed directly using Lorentz-transmission electron microscopy. Among several competing phases, the SkL is promoted over a low-temperature transverse conical state by thermal fluctuations in an intermediate range of magnetic fields.

Controlling the helicity of magnetic skyrmions by electrical field in frustrated magnets

“…proposed that the skyrmion crystal can be stabilized by the frustrated interactions [46], but the following experimental reports on the skyrmions in frustrated systems were very limited [47,48]. It was exciting that very recently the skyrmion crystal was experimentally discovered in the frustrated centrosymmetric triangular-lattice magnet Gd 2 PdSi 3 [49] and breathing kagomé lattice magnet Gd 3 Ru 4 Al 12 [50]. Due to the frustration source, the skyrmions are typically much smaller than the DMI-driven counterpart, and thus contribute to a giant topological Hall effect.…”

Stability and metastability of skyrmions in thin lamellae ofCu2OSeO3

“…It typically consists of a hexagonal array of topologically protected magnetic vortex-like structures that appear in a variety of different materials, usually stabilized by a combination of symmetric exchange, the Dzyaloshinskii-Moriya interaction (DMI), crystal anisotropies, and thermal fluctuations [4]. Since their first discovery in the B20 metal MnSi [6], skyrmions have been found in similar noncentrosymmetric materials such as FeGe [7], Fe 1−x Co x Si [8], Cu 2 OSeO 3 [9], and others [10][11][12], and recently in some centrosymmetric materials where geometric magnetic frustration is thought to play a role [19,20]. They have also been seen in grown thin films and multilayers where interfacial DMI [13][14][15] or a combination of DMI, uniaxial anisotropy, and geometric confinement [16][17][18] help stabilize the skyrmions.…”

Measuring the formation energy barrier of skyrmions in zinc-substituted Cu2OSeO3

“…Skyrmion lattices usually form only in a small region of magnetic field and temperature just below the magnetic ordering temperature, and are typically stabilized by competition between the Dzyaloshinskii-Moriya interaction (DMI), symmetric exchange, and thermal fluctuations 4 . This state was first discovered in the non-centrosymmetric metallic compound MnSi which crystallizes in the P 2 1 3 space group 6 , and has since been found in isostructural materials such as FeGe 7 , Fe 1−x Co x Si 8 , and Cu 2 OSeO 3 9 , in other noncentrosymmetric compounds [10][11][12] , in thin films where skyrmions are stabilized by interfacial DMI [13][14][15] or by a combination of DMI, uniaxial anisotropy and geometric confinement [16][17][18] , and in some centrosymmetric materials where the state is thought to be stabilized by magnetic frustration 19,20 .…”