The promise of high-density and low-energy-consumption devices motivates the search for layered structures that stabilize chiral spin textures such as topologically protected skyrmions. At the same time, recently discovered long-range intrinsic magnetic orders in the two-dimensional van der Waals materials provide a new platform for the discovery of novel physics and effects. Here we demonstrate the Dzyaloshinskii-Moriya interaction and Néeltype skyrmions are induced at the WTe 2 /Fe 3 GeTe 2 interface. Transport measurements show the topological Hall effect in this heterostructure for temperatures below 100 K. Furthermore, Lorentz transmission electron microscopy is used to directly image Néel-type skyrmion lattice and the stripe-like magnetic domain structures as well. The interfacial coupling induced Dzyaloshinskii-Moriya interaction is estimated to have a large energy of 1.0 mJ m −2. This work paves a path towards the skyrmionic devices based on van der Waals layered heterostructures.

Geometric Hall effect is induced by the emergent gauge field experienced by the carriers adiabatically passing through certain real-space topological spin textures, which is a probe to non-trivial spin textures, such as magnetic skyrmions. We report experimental indications of spin-texture topological charges induced in heterostructures of a topological insulator (Bi,Sb)2Te3 coupled to an antiferromagnet MnTe. Through a seeding effect, the pinned spins at the interface leads to a tunable modification of the averaged real-space topological charge. This effect experimentally manifests as a modification of the field-dependent geometric Hall effect when the system is field-cooled along different directions. This heterostructure represents a platform for manipulating magnetic topological transitions using antiferromagnetic order.

opportunities for exploring magnetism, and toward spintronic applications in the 2D limit. [7][8][9] Among all the interface engineered heterostructures based on vdW layered systems, magnetic proximity effect is integral to manipulating spintronic, [10][11][12] superconducting, [13][14][15] and topological phenomena. [16][17][18] Magnetic skyrmions have been well studied due to their nontrivial topology, which leads to many interesting fundamental and dynamical properties. [19][20][21] These have been reported mostly for noncentrosymmteric single crystals, [22][23][24] ultrathin epitaxial system, [25,26] and magnetic multilayers. [27][28][29][30][31] Recently Néel-type skyrmions were observed in a vdW ferromagnet interfaced with an oxidized layer [32] or a transition metal dichalcogenide [33] with a control of the skyrmion phase through tuning of the ferromagnet thickness. Furthermore, with a variety of vdW magnets, skrymions phase could be created in their new interfaces with unique properties.Materials hosting multiple skyrmion phases add richness to the field, with an additional degree of freedom in designing Multiple magnetic skyrmion phases add an additional degree of freedom for skyrmion-based ultrahigh-density spin memory devices. Extending the field to 2D van der Waals magnets is a rewarding challenge, where the realizable degree of freedoms (e.g., thickness, twist angle, and electrical gating) and high skyrmion density result in intriguing new properties and enhanced functionality. In this work, a van der Waals interface, formed by two 2D ferromagnets Cr 2 Ge 2 Te 6 and Fe 3 GeTe 2 with a Curie temperature of ≈65 and ≈205 K, respectively, hosting two groups of magnetic skyrmions, is reported. Two sets of topological Hall effect signals are observed below 6s0 K when Cr 2 Ge 2 Te 6 is magnetically ordered. These two groups of skyrmions are directly imaged using magnetic force microscopy, and supported by micromagnetic simulations. Interestingly, the magnetic skyrmions persist in the heterostructure with zero applied magnetic field. The results are promising for the realization of skyrmionic devices based on van der Waals heterostructures hosting multiple skyrmion phases.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202110583.

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Free-standing, interconnected metallic nanowire networks with density as low as 40 mg/cm 3 have been achieved over cm-scale areas, using electrodeposition into polycarbonate membranes that have been ion-tracked at multiple angles. Networks of interconnected magnetic nanowires further provide an exciting platform to explore 3-dimensional nanomagnetism, where their structure, topology and frustration may be used as additional degrees of freedom to tailor the materials properties. New magnetization reversal mechanisms in cobalt networks are captured by the first-order reversal curve method, which demonstrate the evolution from strong demagnetizing dipolar interactions to intersections-mediated domain wall pinning and propagation, and eventually to shape-anisotropy dominated magnetization reversal. These findings open up new possibilities for 3-dimensional integrated magnetic devices for memory, complex computation, and neuromorphics.

Integration of a quantum anomalous Hall insulator with a magnetically ordered material provides an additional degree of freedom through which the resulting exotic quantum states can be controlled. Here, an experimental observation is reported of the quantum anomalous Hall effect in a magnetically‐doped topological insulator grown on the antiferromagnetic insulator Cr2O3. The exchange coupling between the two materials is investigated using field‐cooling‐dependent magnetometry and polarized neutron reflectometry. Both techniques reveal strong interfacial interaction between the antiferromagnetic order of the Cr2O3 and the magnetic topological insulator, manifested as an exchange bias when the sample is field‐cooled under an out‐of‐plane magnetic field, and an exchange spring‐like magnetic depth profile when the system is magnetized within the film plane. These results identify antiferromagnetic insulators as suitable candidates for the manipulation of magnetic and topological order in topological insulator films.

-When solutions of naphthalene in mixed alkanes or alcohols are irradiated at 315 nm or shorter wavelengths, naphthalene is destroyed by a series of reactions whose rates are greatly accelerated at high pressures. Analyses of the photoproducts recovered from diamond-anvil high pressure cells by gas chromatography-mass spectrometry demonstrate that several reactions are involved: 1) sensitized photolysis of solvent molecules to alkyl and alkoxy radicals; 2) reduction of naphthalene to tetrahydronaphthalene and hydronaphthyl radicals; 3) polymerization of the hydronaphthyl and alkyl radicals to dimers, trimers and higher polymers; 4) photoaddition of solvent radicals to naphthalene; and 5) H-D exchange between naphthalene and the solvents. The dependence of rate of disappearance of naphthalene on the excitation intensity shows that the primary photochemical step involves two-photons and triplet naphthalene intermediates that sensitize production of the free radicals which, at high pressures, are efficient consumers of unsaturated bonds. Implications of these and other phenomena described in the high pressure literature for the stabilities of unsaturated organic compounds at high pressures are discussed. Résumé -Quand le naphthalène en solution dans des mélanges d'alcanes ou d'alcools est irradié à des longueurs d'onde < 315 nm, il est détruit par une série de réactions qui sont fortement accélérées à haute pression. Les analyses GOMS des photoproduits recouvrés après montée à très haute pression (> 5GPa) montrent que plusieurs réactions sont impliquées : 1) la photolyse sensibilisée des molé-cules de solvant en radicaux alkyles et alkoxyles ; 2) la réduction du naphthalène en tétrahydronaphthalène et radicaux hydronaphthyles ; 3) la polymérisation des radicaux hydronaphthyles et alkyles en dimères, trimères et polymères ; 4) la photoaddition des radicaux du solvant sur le naphthalène ; et 5) l'échange H-D entre le naphthalène et les molécules de solvant. La variation de l'intensité d'excitation en fonction de la vitesse de disparition du naphthalène montre que l'étape photochimique primaire est la formation biphotonique des intermédiaires triplets du naphthalène sensibilisant la production des radicaux libres qui, à haute pression, sont des consommateurs efficaces de liaisons insaturées. Les conséquences de ces phénomènes (ainsi que d'autres décrits dans la littérature) sur la stabilité des composés organiques insaturés, à haute pression, sont discutées.Article published online by EDP Sciences and available at http://dx

physical and materials science, but also because of their great potential for energyefficient spintronic applications. [1,2] Blochtype skyrmions were first observed in B20 magnets, [3,4] where the broken inversion symmetry allows for a Dzyaloshinskii-Moriya interaction (DMI), [5,6] leading to the helical alignment of spins. Similarly, in magnetic multilayers, the broken inversion symmetry along the stacking direction also results in an interfacial DMI, stabilizing Néel-type skyrmions. [7] It has also been demonstrated that skyrmions can be created in certain ferromagnets even without significant DMI, stabilized instead by the competition among the uniaxial magnetic anisotropy, dipolar, and exchange interaction. [8][9][10][11][12][13][14][15] For future spintronic devices in which skyrmions are used as information carriers, electrical detection of skyrmions is crucial. At the adiabatic limit, itinerant spins passing through a skyrmion capture an extra Berry phase. As a result, a transverse Hall voltage will be induced in addition to the ordinary and anomalous Hall effects, known as the topological Hall effect (THE). [16] The topological Hall voltage is proportional to the topological charge (skyrmion number) Room-temperature magnetic skyrmion materials exhibiting robust topological Hall effect (THE) are crucial for novel nano-spintronic devices. However, such skyrmion-hosting materials are rare in nature. In this study, a self-intercalated transition metal dichalcogenide Cr 1+x Te 2 with a layered crystal structure that hosts room-temperature skyrmions and exhibits large THE is reported. By tuning the self-intercalate concentration, a monotonic control of Curie temperature from 169 to 333 K and a magnetic anisotropy transition from outof-plane to the in-plane configuration are achieved. Based on the intercalation engineering, room-temperature skyrmions are successfully created in Cr 1.53 Te 2 with a Curie temperature of 295 K and a relatively weak perpendicular magnetic anisotropy. Remarkably, a skyrmion-induced topological Hall resistivity as large as ≈106 nΩ cm is observed at 290 K. Moreover, a sign reversal of THE is also found at low temperatures, which can be ascribed to other topological spin textures having an opposite topological charge to that of the skyrmions. Therefore, chromium telluride can be a new paradigm of the skyrmion material family with promising prospects for future device applications.