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The anomalous Hall effect (AHE) is an intriguing transport phenomenon occurring typically in ferromagnets as a consequence of broken time reversal symmetry and spin-orbit interaction. It can be caused by two microscopically distinct mechanisms, namely, by skew or side-jump scattering due to chiral features of the disorder scattering, or by an intrinsic contribution directly linked to the topological properties of the Bloch states. Here we show that the AHE can be artificially engineered in materials in which it is originally absent by combining the effects of symmetry breaking, spin orbit interaction and proximity-induced magnetism. In particular, we find a strikingly large AHE that emerges at the interface between a ferromagnetic manganite (La_(0.7)Sr_(0.3)MnO_3) and a semimetallic iridate (SrIrO_3). It is intrinsic and originates in the proximity-induced magnetism present in the narrow bands of strong spin-orbit coupling material SrIrO_3, which yields values of anomalous Hall conductivity and Hall angle as high as those observed in bulk transition-metal ferromagnets. These results demonstrate the interplay between correlated electron physics and topological phenomena at interfaces between 3d ferromagnets and strong spin-orbit coupling 5d oxides and trace an exciting path towards future topological spintronics at oxide interfaces. The anomalous Hall effect (AHE) occurs in ferromagnets caused by intrinsic and extrinsic mechanisms. Here, Yoo et al. report large anomalous Hall conductivity and Hall angle at the interface between a ferromagnet La_(0.7)Sr_(0.3M)nO_3 and a semimetallic SrIrO_3, due to the interplay between correlated physics and topological phenomena.

The persistence of ferroelectricity in ultrathin layers relies critically on screening or compensation of polarization charges which otherwise destabilize the ferroelectric state. At surfaces, charged defects play a crucial role in the screening mechanism triggering novel mixed electrochemical-ferroelectric states. At interfaces, however, the coupling between ferroelectric and electrochemical states has remained unexplored. Here, we make use of the dynamic formation of the oxygen vacancy profile in the nanometer-thick barrier of a ferroelectric tunnel junction to demonstrate the interplay between electrochemical and ferroelectric degrees of freedom at an oxide interface. We fabricate ferroelectric tunnel junctions with a ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ bottom electrode and ${\mathrm{BaTiO}}_{3}$ ferroelectric barrier. We use poling strategies to promote the generation and transport of oxygen vacancies at the metallic top electrode. Generated oxygen vacancies control the stability of the ferroelectric polarization and modify its coercive fields. The ferroelectric polarization, in turn, controls the ionization of oxygen vacancies well above the limits of thermodynamic equilibrium, triggering the build up of a Schottky barrier at the interface which can be turned on and off with ferroelectric switching. This interplay between electronic and electrochemical degrees of freedom yields very large values of the electroresistance (more than ${10}^{6}%$ at low temperatures) and enables a controlled switching between clockwise and counterclockwise switching modes in the same junction (and consequently, a change of the sign of the electroresistance). The strong coupling found between electrochemical and electronic degrees of freedom sheds light on the growing debate between resistive and ferroelectric switching in ferroelectric tunnel junctions, and moreover, can be the source of novel concepts in memory devices and neuromorphic computing.

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 LaSrMnO electrodes separated by an ultrathin ferroelectric BaTiO tunnel 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., Work supported by Spanish MINECO through grants MAT2014-52405-C02-01 and MAT2014-52405-C02-02, MAT2015-066888-C3-1-R, MAT2015-066888-C3-3-R (MINECO/FEDER) and CAM S2013/MIT-2740. Research at ORNL sponsored by the US Department of Energy (DOE), Basic Energy Sciences (BES), M.V. acknowledges support from Fundación BBVA. G.S. and M.C. acknowledge support from ERC Starting Investigator Grant #239739 STEMOX. J.I.B. acknowledges the Spanish Supercomputing Network (RES) and CeSViMa (project FI-2016-2-0006). J.S. thanks Université Paris Saclay (DÁlembert Program) and CNRS for financing his stay at CNRS Thales.

In artificial multiferroics hybrids consisting of ferromagnetic La_(0.7)Sr_(0.3)MnO_(3) (LSMO) and ferroelectric BaTiO_(3) epitaxial layers, net Ti moments are found from polarized resonant soft x-ray reflectivity and absorption. The Ti dichroic reflectivity follows the Mn signal during the magnetization reversal, indicating exchange coupling between the Ti and Mn ions. However, the Ti dichroic reflectivity shows stronger temperature dependence than the Mn dichroic signal. Besides a reduced ferromagnetic exchange coupling in the interfacial LSMO layer, this may also be attributed to a weak Ti-Mn exchange coupling that is insufficient to overcome the thermal energy at elevated temperatures.

Controlling magnetic anisotropy is an important objective towards engineering novel magnetic device concepts in oxide electronics. In thin film manganites, magnetic anisotropy is weak and it is primarily determined by the substrate, through induced structural distortions resulting from epitaxial mismatch strain. On the other hand, in cobaltites, with a stronger spin orbit interaction, magnetic anisotropy is typically much stronger. In this paper, we show that interfacing LaSrMnO (LSMO) with an ultrathin LaCoO (LCO) layer drastically modifies the magnetic anisotropy of the manganite, making it independent of the substrate and closer to the magnetic isotropy characterizing its rhombohedral structure. Ferromagnetic resonance measurements evidence a tendency of manganite magnetic moments to point out-of-plane suggesting non collinear magnetic interactions at the interface. These results may be of interest for the design of oxide interfaces with tailored magnetic structures for new oxide devices., Work at UCM supported by Spanish MINECO through Grant Nos. MAT2014-52405-C02-01 and MAT2014-52405-C02-02 and by CAM through Grant No. CAM S2013/MIT-2740. M.V. and M.C. acknowledge support from Fundación BBVA and from MINECO through Grant No. MAT2015-066888-C3-3-R. J.S. thanks the University Paris-Saclay (D’Alembert program) and CNRS for financing his stay at CNRS/Thales. T.F. acknowledges support from the Hungarian Research Fund OTKA No. K107228.

Here we study the electronic properties of cuprate/manganite interfaces. By means of atomic resolution electron microscopy and spectroscopy, we produce a subnanometer scale map of the transition metal oxidation state profile across the interface between the high $T_c$ superconductor YBa$_2$Cu$_3$O$_{7-\delta}$ and the colossal magnetoresistance compound (La,Ca)MnO$_3$. A net transfer of electrons from manganite to cuprate with a peculiar non-monotonic charge profile is observed. Model calculations rationalize the profile in terms of the competition between standard charge transfer tendencies (due to band mismatch), strong chemical bonding effects across the interface, and Cu substitution into the Mn lattice, with different characteristic length scales., Comment: 11+7 pages, 3+2 figures

The magnetism of La0.7Ca0.3MnO3 (LCMO) epitaxial thin films grown on SrTiO3 (STO) and BaTiO3 (BTO) substrates is studied using polarized neutron reflectometry (PNR) and ferromagnetic resonance (FMR) techniques. In LCMO/BTO, PNR reveals a strongly suppressed magnetization of 300 kA/m, equivalent to a magnetic moment of 2 μB/Mn, throughout the LCMO layer, amounting to half the expected value. The largest suppression occurs near the interface with BTO, with magnetization values of 50 kA/m, equivalent to 0.3 μB/Mn. FMR is observable at 8.9 GHz only around the [110] crystallographic direction in thin LCMO/BTO. The resonance barely shifts as the applied field is rotated away from [110]. The FMR results are analyzed in terms of magnetoelastic anisotropy and compared to LCMO/STO grown under the same conditions. A two-layer magnetization model is proposed, based on strong out-of-plane anisotropy near the BTO interface and shown to qualitatively explain the main characteristics of the FMR results.

An unusual conducting surface state can be produced in SrTiO3 substrates by irradiation with Argon ions from a plasma source, at low energy and high doses. The effects of irradiation are analyzed here by atomic force microscopy (AFM) and aberration corrected scanning transmission electron microscopy (STEM) combined with electron energy loss spectroscopy (EELS). Depth sensitive studies demonstrate the existence of a heavily damaged surface layer and an oxygen vacancy rich layer immediately underneath, both induced during the irradiation process. We find a clear dependence of the Ti oxidation state with the depth, with a very intense Ti 3 þ component near the surface. Oxygen vacancies act as n-type doping by releasing electrons into the lattice and producing an insulator-to-metal transition, which explains the unusual metallic behavior of these samples. Published by Elsevier B.V.