A superconducting interfaceInterfaces between materials can harbor quantum states that belong to neither of the materials. A classic example is the superconducting interface between two insulating ...oxides, LaAlO3 and SrTiO3, with a critical temperature of around 200 millikelvin. Liu et al. observed superconductivity at a different interface—formed between KTaO3 as a substrate and an overlayer of either EuO or LaAlO3—at a considerably higher temperature of about 2 kelvin. Transport measurements displayed anisotropy, which may indicate an unusual superconducting state.Science, this issue p. 716The distinctive electronic structure found at interfaces between materials can allow unconventional quantum states to emerge. Here we report on the discovery of superconductivity in electron gases formed at interfaces between (111)-oriented KTaO3 and insulating overlayers of either EuO or LaAlO3. The superconducting transition temperature, as high as 2.2 kelvin, is about one order of magnitude higher than that of the LaAlO3/SrTiO3 system. Notably, similar electron gases at KTaO3 (001) interfaces remain normal down to 25 millikelvin. The critical field and current-voltage measurements indicate that the superconductivity is two-dimensional. In EuO/KTaO3 (111) samples, a spontaneous in-plane transport anisotropy is observed before the onset of superconductivity, suggesting the emergence of a distinct “stripe”-like phase, which is also revealed near the critical field.
The conductance confined at the interface of complex oxide heterostructures provides new opportunities to explore nanoelectronic as well as nanoionic devices. Herein we show that metallic interfaces ...can be realized in SrTiO3-based heterostructures with various insulating overlayers of amorphous LaAlO3, SrTiO3, and yttria-stabilized zirconia films. On the other hand, samples of amorphous La7/8Sr1/8MnO3 films on SrTiO3 substrates remain insulating. The interfacial conductivity results from the formation of oxygen vacancies near the interface, suggesting that the redox reactions on the surface of SrTiO3 substrates play an important role.
Grouping different transition metal oxides together by interface engineering is an important route toward emergent phenomenon. While most of the previous works focused on the interface effects in ...perovskite/perovskite heterostructures, here we reported on a symmetry mismatch-driven spin reorientation toward perpendicular magnetic anisotropy in perovskite/brownmillerite heterostructures, which is scarcely seen in tensile perovskite/perovskite heterostructures. We show that alternately stacking perovskite La
Sr
MnO
and brownmillerite LaCoO
causes a strong interface reconstruction due to symmetry discontinuity at interface: neighboring MnO
octahedra and CoO
tetrahedra at the perovskite/brownmillerite interface cooperatively relax in a manner that is unavailable for perovskite/perovskite interface, leading to distinct orbital reconstructions and thus the perpendicular magnetic anisotropy. Moreover, the perpendicular magnetic anisotropy is robust, with an anisotropy constant two orders of magnitude greater than the in-plane anisotropy of the perovskite/perovskite interface. The present work demonstrates the great potential of symmetry engineering in designing artificial materials on demand.
The magnetocaloric effect (MCE) of RNi2Si2 (R=Dy, Ho, Er) compounds with the ThCr2Si2-type body-centered tetragonal structure are investigated. RNi2Si2 compounds are antiferromagnetic (AFM) with Néel ...temperature TN=6.5K, 4.9K, and 3.5K, respectively. A field-induced metamagnetic transition from AFM-to-ferromagnetic (FM) state is found below TN, which leads to a large MCE around the TN. The maximal values of magnetic entropy change (ΔSM) for RNi2Si2 (R=Dy, Ho, Er) reach −6.9, −10.9, and −15.1Jkg−1K−1 and −21.3, −21.7, and −21.3Jkg−1K−1 without thermal and magnetic hysteresis losses for the field changes of 0–2T and 0–5T, respectively. The large ΔSM is associated with the field-induced first-order AFM–FM metamagnetic transition and low critical field. The excellent MCE under low field change without hysteresis loss suggests that RNi2Si2 (R=Dy, Ho, Er) can be an appropriate candidate for magnetic refrigerant in liquid helium temperature ranges.
•Magnetocaloric effect (MCE) of RNi2Si2 (R=Dy, Ho, Er) are investigated.•The maximum ΔSM for ErNi2Si2 is 15.1Jkg−1K−1 under the field change of 0–2T.•RNi2Si2 compounds show very low thermal and magnetic hysteresis losses.
Particle‐like magnetic textures with nanometric sizes, such as skyrmions, are potentially suitable for designing high‐efficiency information bits in future spintronics devices. In general, the ...Dzyaloshinskii–Moriya interactions and dipolar interactions are the dominant factors for generating nonlinear spin configurations. However, to stabilize the topological skyrmions, an external magnetic field is usually required. In this study, the spontaneous emergence of skyrmions is directly observed, together with the unique successive topological domain evolution during the spin reorientation transition in a neodymium–cobalt (NdCo5) rare‐earth magnet. On decreasing the temperature, nanometric skyrmion lattices evolve into enclosed in‐plane domains (EIPDs) similar to mini bar‐magnets with size below 120 nm. The internal magnetization rotates with magnetic anisotropy, demonstrating the ability to manipulate the mini bar‐magnets. The nanoscale EIPD lattices remain robust over the wide temperature range of 241–167 K, indicating the possibility of high‐density in‐plane magnetic information storage. The generation of spontaneous magnetic skyrmions and the successive domain transformation in the traditional NdCo5 rare‐earth magnet may prompt application exploration for topological magnetic spin textures with novel physical mechanisms in versatile magnets.
Spontaneous magnetic biskyrmion lattices and the successive transformation into enclosed in‐plane domains over a broad temperature range of 120–282 K is directly observed by in situ cooling a hexagonal rare‐earth NdCo5 alloy in Lorentz TEM. The ability to manipulate topological magnetization by anisotropy invites application exploration of novel topological magnetic spin textures and physical mechanisms in rare‐earth magnets.
With the help of the two-dimensional electron gas (2DEG) at the LaAlO3–SrTiO3 interface, spin and charge currents can be interconverted. However, the conversion efficiency has been strongly depressed ...by LaAlO3, which blocks spin transmission. It is therefore highly desired to explore 2DEGs sandwiched between ferromagnetic insulators that are transparent for magnons. By constructing epitaxial heterostructure with ferromagnetic EuO, which is conducting for spin current but insulating for electric current, and KTaO3, we successfully obtained the 2DEGs, which can receive thermally injected spin current directly from EuO and convert the spin current to charge current via inverse Edelstein effect of the interface. Strong dependence of the spin Seebeck coefficient on the layer thickness of EuO is further observed and the propagation length for non-equilibrium magnons in EuO has been determined. The present work demonstrates the great potential of the 2DEGs formed by ferromagnetic oxides for spin caloritronics.
The free-field switching of the perpendicular magnetization by the out-of-plane polarized spin current induced spin-orbit torque makes it a promising technology for developing high-density memory and ...logic devices. The materials intrinsically with low symmetry are generally utilized to generate the spin current with out-of-plane spin polarization. However, the generation of the out-of-plane polarized spin current by engineering the symmetry of materials has not yet been reported. Here, we demonstrate that paramagnetic CaRuO3 films are able to generate out-of-plane polarized spin current by engineering the crystal symmetry. The non-uniform oxygen octahedral tilt/rotation along film’s normal direction induced by oxygen octahedral coupling near interface breaks the screw-axis and glide-plane symmetries, which gives rise to a significant out-of-plane polarized spin current. This spin current can drive field-free spin-orbit torque switching of perpendicular magnetization with high efficiency. Our results offer a promising strategy based on crystal symmetry design to manipulate spin current and could have potential applications in advanced spintronic devices.The authors realize generation of out-of-plane polarized spin current in perovskite oxide CaRuO3 with reduced crystal symmetry by engineering the oxygen octahedra, which can drive efficient field-free switching of perpendicular magnetization.
Platinum metal, being nonmagnetic and with a strong spin-orbit coupling interaction, has been deposited on weak ferromagnetic Bi0.9La0.1FeO3 thin films. The Hall effect is studied as a function of ...the polarization direction of multiferroic Bi0.9La0.1FeO3 thin films, as well as magnetic field (H) and temperature (T). For the two polarization directions, besides the obvious difference of the anomalous Hall resistance RAH, it increases sharply with decreasing temperature, and even changes sign, thus violating the conventional expression. This observations indicate local magnetic moments in Pt caused by the local electric fields at the interface of Bi0.9La0.1FeO3 films. Also, possible proximity effects and induced magnetic ordering in Pt on weak ferromagnetic Bi0.9La0.1FeO3 thin films of both upward and downward polarization states may exist and their contribution to the spin-related measurements should not be neglected.
A magnetic tuning of the photovoltaic effect is demonstrated for the Schottky junction formed by a ferromagnetic (FM) layer and silicon. Obvious anisotropic magnetic photovoltaic effects (AMV) are ...gained not only in the FM layer but also in the Si substrate though the latter is non‐magnetic. Key factors determining the AMV of Si are identified.
In this study, we show the real-space observation of the magnetic domain configuration in amorphous Ce14Fe80B6 ribbon using Lorentz transmission electron microscopy. Cross-tie domain walls composed ...of magnetic vortices (Vs) and antivortices (AVs) are observed. The evolution of Vs/AVs manipulated by temperature, in-plane magnetic field, and electrical current is clearly demonstrated. Magnetic V nucleation and annihilation in pair are observed because of the stimulus of external fields.
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