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We demonstrate the fabrication of field-effect transistors based on single-layer MoS2and a thin layer of BaTiO3(BTO) dielectric, isolated from its parent epitaxial template substrate. Thin BTO provides an ultrahigh-κ gate dielectric effectively screening Coulomb scattering centers. These devices show mobilities substantially larger than those obtained with standard SiO2dielectrics and comparable with values obtained with hexagonal boron nitride, a dielectric employed for fabrication of high-performance two-dimensional (2D) based devices. Moreover, the ferroelectric character of BTO induces a robust hysteresis of the current vs gate voltage characteristics, attributed to its polarization switching. This hysteresis is strongly suppressed when the device is warmed up above the tetragonal-to-cubic transition temperature of BTO that leads to a ferroelectric-to-paraelectric transition. This hysteretic behavior is attractive for applications in memory storage devices. Our results open the door to the integration of a large family of complex oxides exhibiting strongly correlated physics in 2D-based devices.

Swirling spin textures, including topologically nontrivial states, such as skyrmions, chiral domain walls, and magnetic vortices, have garnered significant attention within the scientific community due to their appeal from both fundamental and applied points of view. However, their creation, controlled manipulation, and stability are typically constrained to certain systems with specific crystallographic symmetries, bulk or interface interactions, and/or a precise stacking sequence of materials. Recently, a new approach has shown potential for the imprint of magnetic radial vortices in soft ferromagnetic compounds making use of the stray field of YBa2Cu3O7-δsuperconducting microstructures in ferromagnet/superconductor (FM/SC) hybrids at temperatures below the superconducting transition temperature (TC). Here, we explore the lower size limit for the imprint of magnetic radial vortices in square and disc shaped structures as well as the persistence of these spin textures above TC, with magnetic domains retaining partial memory. Structures with circular geometry and with FM patterned to smaller radius than the superconductor island facilitate the imprinting of magnetic radial vortices and improve their stability above TC, in contrast to square structures where the presence of magnetic domains increases the dipolar energy. Micromagnetic modeling coupled with a SC field model reveals that the stabilization mechanism above TCis mediated by microstructural defects. Superconducting control of swirling spin textures, and their stabilization above the superconducting transition temperature by means of defect engineering holds promising prospects for shaping superconducting spintronics based on magnetic textures.

Strong electronic correlations can produce remarkable phenomena such as metal–insulator transitions and greatly enhance superconductivity, thermoelectricity or optical nonlinearity. In correlated systems, spatially varying charge textures also amplify magnetoelectric effects or electroresistance in mesostructures. However, how spatially varying spin textures may influence electron transport in the presence of correlations remains unclear. Here we demonstrate a very large topological Hall effect (THE) in thin films of a lightly electron-doped charge-transfer insulator, (Ca,Ce)MnO3. Magnetic force microscopy reveals the presence of magnetic bubbles, whose density as a function of magnetic field peaks near the THE maximum. The THE critically depends on carrier concentration and diverges at low doping, near the metal–insulator transition. We discuss the strong amplification of the THE by correlation effects and give perspectives for its non-volatile control by electric fields.

Planar Josephson junctions with Nb electrodes and a composite weak link barrier combining heavy metal Pt and ferrimagnetic Y3Fe5O12enable a large supercurrent diode effect at 4He fridge temperatures in the absence of an applied magnetic field.

The peculiar features of domain walls observed in ferroelectrics make them promising active elements for next-generation non-volatile memories, logic gates and energy-harvesting devices. Although extensive research activity has been devoted recently to making full use of this technological potential, concrete realizations of working nanodevices exploiting these functional properties are yet to be demonstrated. Here, we fabricate a multiferroic tunnel junction based on ferromagnetic La0.7Sr0.3MnO3electrodes separated by an ultrathin ferroelectric BaTiO3tunnel barrier, where a head-to-head domain wall is constrained. An electron gas stabilized by oxygen vacancies is confined within the domain wall, displaying discrete quantum-well energy levels. These states assist resonant electron tunnelling processes across the barrier, leading to strong quantum oscillations of the electrical conductance.

Abstract

The new field of nano-ionics is expected to yield large improvements in the performance of oxide-based energy generation and storage devices based on exploiting size effects in ion conducting materials. The search for novel materials with enhanced ionic conductivity for application in energy devices has uncovered an exciting new facet of oxide interfaces. With judicious choice of the constituent materials, oxide heterostructures can exhibit enhanced ion mobility compared to the bulk counterparts. Here we review recent experimental and theoretical progress on enhancement of oxide-ion conductivity arising in oxide ultrathin layers and at their interfaces, and describe the different scenarios, space-charge effects, epitaxial strain, and atomic reconstruction at the interface, proposed to account for the observed conductivity enhancement.

Different compositions in the Gd2-yLayZr2O7 solid solution (0 {less than or equal to} y {less than or equal to} 1) were prepared at room-temperature, by mechanically milling stoichiometric mixtures of the corresponding oxides. We found that irrespective of their lanthanum content, as-prepared powder samples consist of single-phase anion deficient fluorite materials, although post-milling thermal treatments at 1200oC facilitates the long-range ordering of cations and anion vacancies characteristic of pyrochlores for y {greater than or equal to} 0.4. Interestingly, activation energy for oxygen migration in the series decreases from 1.13 {plus minus} 0.02 eV (Gd2Zr2O7) to 0.84 {plus minus} 0.03 eV (GdLaZr2O7) as La-content and the RA/RB ratio increase. These results are explained in terms of weaker ion-ion interactions in better ordered and highlight the importance of structural ordering/disordering in determining the dynamics of mobile oxygen ions.

In the version of this Letter originally published, Hiroshi Kohno’s affiliation was incorrectly listed as Department of Earth and Space Science, Graduate School of Science, Osaka University, Osaka, Japan; it should have been Department of Physics, Nagoya University, Nagoya, Japan. This has been corrected in all versions of the Letter.

All oxide magnetic tunnel junctions based on epitaxial La0.7Ca0.3MnO3(LCMO)(8 nm)/PrBa2Cu3O7(PBCO) (3–8 nm)/LCMO(25–50 nm) heterostructures grown on (100) SrTiO3are examined. Manganite electrodes show large (bulk‐like) magnetic moments and exhibit different magnetic anisotropies with different easy axes directions. A form of low dimensional magnetism is induced at the interfaces by the superexchange interaction across the reconstructed bonds. It acts as an exchange spring, driving ferromagnetic coupling between the electrodes. Resistance versus magnetic field loops demonstrate that the interfacial coupling strength depends on electric field through its effect on electronic reconstruction and orbital hierarchy at the interface. The electrically controlled magnetic coupling between the magnetic moments of the electrodes signals a new path toward low dissipation spintronics. The emergent electronic states at the interfacebetween correlated oxides are a source of exciting novel device concepts. The induced magnetism resulting from orbital reconstruction at the barrier/electrode interfaces of a magnetic tunnel junction triggers a novel form of ferromagnetic coupling between magnetic electrodes has been showed. This coupling is electrically controlled and enables electric field switching of the magnetization, drawing a new strategy toward low dissipation spintronics.

Different compositions in the Gd2-yLayZr2O7 solid solution (0 {less than or equal to} y {less than or equal to} 1) were prepared at room-temperature, by mechanically milling stoichiometric mixtures of the corresponding oxides. We found that irrespective of their lanthanum content, as-prepared powder samples consist of single-phase anion deficient fluorite materials, although post-milling thermal treatments at 1200ºC facilitates the long-range ordering of cations and anion vacancies characteristic of pyrochlores for y {greater than or equal to} 0.4. Interestingly, activation energy for oxygen migration in the series decreases from 1.13 {plus minus} 0.02 eV (Gd2Zr2O7) to 0.84 {plus minus} 0.03 eV (GdLaZr2O7) as La-content and the RA/RB ratio increase. These results are explained in terms of weaker ion-ion interactions in better ordered and highlight the importance of structural ordering/disordering in determining the dynamics of mobile oxygen ions.

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