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Producing hydrogen by water electrolysis suffers from the kinetic barriers in the oxygen evolution reaction (OER) that limits the overall efficiency. With spin-dependent kinetics in OER, to manipulate the spin ordering of ferromagnetic OER catalysts (e.g., by magnetization) can reduce the kinetic barrier. However, most active OER catalysts are not ferromagnetic, which makes the spin manipulation challenging. In this work, we report a strategy with spin pinning effect to make the spins in paramagnetic oxyhydroxides more aligned for higher intrinsic OER activity. The spin pinning effect is established in oxideFM/oxyhydroxide interface which is realized by a controlled surface reconstruction of ferromagnetic oxides. Under spin pinning, simple magnetization further increases the spin alignment and thus the OER activity, which validates the spin effect in rate-limiting OER step. The spin polarization in OER highly relies on oxyl radicals (O∙) created by 1st dehydrogenation to reduce the barrier for subsequent O-O coupling.

EuB6, as a magnetic Weyl semimetal, has attracted much attention in recent years due to its rich intriguing physical properties, especially the colossal negative magnetoresistance (CNMR) exceeding −80% and the topological phase transition. Yet, the underlying mechanism of the CNMR in EuB6 is still controversial. In this work, the CNMR with a maximum value of −88.4% and Hall resistivity without linear dependence on the magnetic field are both observed to indicate the existence of a weak ferromagnetic order below 50 K. The effective carrier concentration can be modulated by both temperatures and external magnetic fields. Moreover, the angle-resolved photoelectron spectroscopy results demonstrate the gradual band splitting and crossing near the Fermi level below 15 K, and the field-dependent Kelvin probe force microscope results confirm the field-induced variation of the Fermi level at different temperatures. Furthermore, by integrating those results with the monotonic increment relationship between the effective carrier concentration and the field-induced magnetization ratio, it is concluded that the magnetic field-induced topological phase transition is the main mechanism for the CNMR in EuB6, which is helpful to understand the exotic transport properties in magnetic topological materials. Our findings provide a route for exploring and manipulating the topology-related transport properties via the external magnetic field in other systems with strong correlation between magnetism and topological states. [ABSTRACT FROM AUTHOR]

Few-layer two-dimensional (2D) semiconductor nanosheets with a layer-dependent band gap are attractive building blocks for large-area thin-film electronics. A general approach is developed to fast prepare uniform and phase-pure 2H-WSe2 semiconducting nanosheets at a large scale, which involves the supercritical carbon dioxide (SC-CO2) treatment and a mild sonication-assisted exfoliation process in aqueous solution. The as-prepared 2H-WSe2 nanosheets preserve the intrinsic physical properties and intact crystal structures, as confirmed by Raman, x-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscope (STEM). The uniform 2H-WSe2 nanosheets can disperse well in water for over six months. Such good dispersivity and uniformity enable these nanosheets to self-assembly into thickness-controlled thin films for scalable fabrication of large-area arrays of thin-film electronics. The electronic transport and photoelectronic properties of the field-effect transistor based on the self-assembly 2H-WSe2 thin film have also been explored. [ABSTRACT FROM AUTHOR]

EuB6, as a magnetic Weyl semimetal, has attracted much attention in recent years due to its rich intriguing physical properties, especially the colossal negative magnetoresistance (CNMR) exceeding −80% and the topological phase transition. Yet, the underlying mechanism of the CNMR in EuB6 is still controversial. In this work, the CNMR with a maximum value of −88.4% and Hall resistivity without linear dependence on the magnetic field are both observed to indicate the existence of a weak ferromagnetic order below 50 K. The effective carrier concentration can be modulated by both temperatures and external magnetic fields. Moreover, the angle-resolved photoelectron spectroscopy results demonstrate the gradual band splitting and crossing near the Fermi level below 15 K, and the field-dependent Kelvin probe force microscope results confirm the field-induced variation of the Fermi level at different temperatures. Furthermore, by integrating those results with the monotonic increment relationship between the effective carrier concentration and the field-induced magnetization ratio, it is concluded that the magnetic field-induced topological phase transition is the main mechanism for the CNMR in EuB6, which is helpful to understand the exotic transport properties in magnetic topological materials. Our findings provide a route for exploring and manipulating the topology-related transport properties via the external magnetic field in other systems with strong correlation between magnetism and topological states. [ABSTRACT FROM AUTHOR]

With the interplay between magnetism and topological bands, magnetic kagome semimetals provide promising platforms for exploring exotic correlated electronic states and quantum phenomena such as anomalous Hall effect, quantum spin liquid, and unconventional magnetoresistance, as well as driving advances in electronic and spintronic applications. Here, a field‐induced butterfly‐like anomalous anisotropic magnetoresistance (AMR) effect in an intriguing kagome semimetal Co3In2S2 is reported. The kagome‐lattice Co3In2S2 single crystals are synthesized via a polycrystal‐source chemical vapor transport approach, possessing a high carrier mobility reaching 104 cm2V−1s−1. The Co3In2S2 single crystal exhibits a canted antiferromagnetic state below 5 K, but intriguingly, it is easily transformed into a ferromagnetic state under a small external magnetic field. Furthermore, the planar Hall effect (PHE) is detected, stemming from the complex contribution of field‐induced ferromagnetism and orbital magnetoresistance. Remarkably, as the magnetic field increases, the low‐temperature magnetoresistance behavior of the Co3In2S2 reveals a butterfly‐like AMR effect with a maximum value of 850%, exhibiting a superposition of the two‐, four‐, and six‐fold AMR terms. Band structure calculations suggest that such a field‐induced butterfly‐like AMR effect may originate from the modulations of the electronic structure near the Fermi level by the magnetic moment. The findings offer a valuable platform for understanding the anomalous AMR effect and for the development of advanced spintronic devices. [ABSTRACT FROM AUTHOR]

With a nontrivial topological band and intrinsic magnetic order, two-dimensional (2D) MnBi 2 Te 4 -family materials exhibit great promise for exploring exotic quantum phenomena and potential applications. However, the synthesis of 2D MnBi 2 Te 4 -family materials via chemical vapor deposition (CVD), which is essential for advancing device applications, still remains a significant challenge since it is difficult to control the reactions among multi-precursors and form pure phases. Here, we report a controllable synthesis of high-quality magnetic topological insulator MnBi 2 Te 4 and MnBi 4 Te 7 multilayers via an evaporation-rate-controlled CVD approach. The multilayers are grown on a mica substrate epitaxially, exhibiting a regular triangle shape. By controlling growth temperatures, the thickness and lateral size of the 2D MnBi 2 Te 4 are well regulated. Furthermore, the magneto-transport measurements clearly reveal multistep spin-flop transitions for both odd- and even-number-layered MnBi 2 Te 4 multilayers. Our study marks a significant stride toward future transformative applications in devices based on high-quality, edge- and thickness-controlled 2D magnetic topological quantum materials.

Van der Waals (vdW) ferromagnetic materials have emerged as a promising platform for the development of 2D spintronic devices. However, studies to date are restricted to vdW ferromagnetic materials with low Curie temperature (T c ) and small magnetic anisotropy. Here, a chemical vapor transport method is developed to synthesize a high-quality room-temperature ferromagnet, Fe 3 GaTe 2 (c-Fe 3 GaTe 2 ), which boasts a high T c = 356 K and large perpendicular magnetic anisotropy. Due to the planar symmetry breaking, an unconventional room-temperature antisymmetric magnetoresistance (MR) is first observed in c-Fe 3 GaTe 2 devices with step features, manifesting as three distinctive states of high, intermediate, and low resistance with the sweeping magnetic field. Moreover, the modulation of the antisymmetric MR is demonstrated by controlling the height of the surface steps. This work provides new routes to achieve magnetic random storage and logic devices by utilizing the room-temperature thickness-controlled antisymmetric MR and further design room-temperature 2D spintronic devices based on the vdW ferromagnet c-Fe 3 GaTe 2 ., (© 2024 Wiley‐VCH GmbH.)