Magnetic skyrmions are topologically stable swirling spin textures with particle-like character, and have been intensively studied as a candidate of high-density information bit. While magnetic skyrmions were originally discovered in noncentrosymmetric systems with Dzyaloshinskii-Moriya interaction, recently a nanometric skyrmion lattice has also been reported for centrosymmetric rare-earth compounds, such as Gd₂PdSi₃ and GdRu₂Si₂. For the latter systems, a distinct skyrmion formation mechanism mediated by itinerant electrons has been proposed, and the search of a simpler model system allowing for a better understanding of their intricate magnetic phase diagram is highly demanded. Here, we report the discovery of square and rhombic lattices of nanometric skyrmions in a centrosymmetric binary compound EuAl₄, by performing small-angle neutron and resonant elastic X-ray scattering experiments. Unlike previously reported centrosymmetric skyrmion-hosting materials, EuAl₄ shows multiple-step reorientation of the fundamental magnetic modulation vector as a function of magnetic field, probably reflecting a delicate balance of associated itinerant-electron-mediated interactions. The present results demonstrate that a variety of distinctive skyrmion orders can be derived even in a simple centrosymmetric binary compound, which highlights rare-earth intermetallic systems as a promising platform to realize/control the competition of multiple topological magnetic phases in a single material.

The formation of the triangular Skyrmion lattice is found in a tetragonal polar magnet ${\mathrm{VOSe}}_2{\mathrm{O}}_5$. By magnetization and small-angle neutron scattering measurements on the single crystals, we identify a cycloidal spin state at zero field and a Néel-type Skyrmion-lattice phase under a magnetic field along the polar axis. Adjacent to this phase, another magnetic phase of an incommensurate spin texture is identified at lower temperatures, tentatively assigned to a square Skyrmion-lattice phase. These findings exemplify the versatile features of Néel-type Skyrmions in bulk materials, and provide a further opportunity to explore the physics of topological spin textures in polar magnets.

We report the discovery of topological magnetism in the candidate magnetic Weyl semimetal CeAlGe. Using neutron scattering we find this system to host several incommensurate, square-coordinated multi-$\overrightarrow{k}$ magnetic phases below $T_N$. The topological properties of a phase stable at intermediate magnetic fields parallel to the $c$ axis are suggested by observation of a topological Hall effect. Our findings highlight CeAlGe as an exceptional system for exploiting the interplay between the nontrivial topologies of the magnetization in real space and Weyl nodes in momentum space.

We report a proximity-driven large anomalous Hall effect in all-telluride heterostructures consisting of the ferromagnetic insulator ${\mathrm{Cr}}_2{\mathrm{Ge}}_2{\mathrm{Te}}_6$ and topological insulator ${(\mathrm{Bi},\mathrm{Sb})}_2{\mathrm{Te}}_3$. Despite small magnetization in the ${(\mathrm{Bi},\mathrm{Sb})}_2{\mathrm{Te}}_3$ layer, the anomalous Hall conductivity reaches a large value of $0.2e^2/h$ in accord with a ferromagnetic response of the ${\mathrm{Cr}}_2{\mathrm{Ge}}_2{\mathrm{Te}}_6$. The results show that the exchange coupling between the surface state of the topological insulator and the proximitized ${\mathrm{Cr}}_2{\mathrm{Ge}}_2{\mathrm{Te}}_6$ layer is effective and strong enough to open the sizable exchange gap in the surface state.

Magnetic skyrmions are vortexlike topological spin textures often observed in structurally chiral magnets with Dzyaloshinskii-Moriya interaction. Among them, Co-Zn-Mn alloys with a $\beta$-Mn-type chiral structure host skyrmions above room temperature. In this system, it has recently been found that skyrmions persist over a wide temperature and magnetic field region as a long-lived metastable state, and that the skyrmion lattice transforms from a triangular lattice to a square one. To obtain perspective on chiral magnetism in Co-Zn-Mn alloys and clarify how various properties related to the skyrmion vary with the composition, we performed systematic studies on ${\mathrm{Co}}_{10}{\mathrm{Zn}}_{10}$, ${\mathrm{Co}}_9{\mathrm{Zn}}_9{\mathrm{Mn}}_2$, ${\mathrm{Co}}_8{\mathrm{Zn}}_8{\mathrm{Mn}}_4$, and ${\mathrm{Co}}_7{\mathrm{Zn}}_7{\mathrm{Mn}}_6$ in terms of magnetic susceptibility and small-angle neutron scattering measurements. Robust metastable skyrmions with extremely long lifetime are commonly observed in all the compounds. On the other hand, the preferred orientation of the helimagnetic propagation vector and its temperature dependence dramatically change upon varying the Mn concentration. The robustness of the metastable skyrmions in these materials is attributed to topological nature of the skyrmions as affected by structural and magnetic disorder. Magnetocrystalline anisotropy as well as magnetic disorder due to frustrated Mn spins play crucial roles in giving rise to the observed change in helical states and corresponding skyrmion lattice form.

Magnetic skyrmions, topological vortex-like spin textures, garner significant interest due to their unique properties and potential applications in nanotechnology. While they typically form a hexagonal crystal with distinct internal magnetisation textures known as Bloch- or Néel-type, recent theories suggest the possibility for direct transitions between skyrmion crystals of different lattice structures and internal textures. To date however, experimental evidence for these potentially useful phenomena have remained scarce. Here, we discover the polar tetragonal magnet EuNiGe₃ to host two hybrid skyrmion phases, each with distinct internal textures characterised by anisotropic combinations of Bloch- and Néel-type windings. Variation of the magnetic field drives a direct transition between the two phases, with the modification of the hybrid texture concomitant with a hexagonal-to-square skyrmion crystal transformation. We explain these observations with a theory that includes the key ingredients of momentum-resolved Ruderman–Kittel–Kasuya–Yosida and Dzyaloshinskii-Moriya interactions that compete at the observed low symmetry magnetic skyrmion crystal wavevectors. Our findings underscore the potential of polar magnets with rich interaction schemes as promising for discovering new topological magnetic phases.