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© 2015 American Physical Society. We acknowledge financial support from the Spanish MINECO through grants (MAT2012-33207, MAT2011- 27470-C02, MAT2012-37638 and Consolider Ingenio 2010 - CSD2009-00013 (Imagine)), from CAM through Grant No. S2009/MAT-1756 (Phama) and Basque Government (PI2011- 1). Financial support from EC through FEDER program and Marie Curie Actions (256470-ITAMOSCINOM) is also acknowledged. C.M.B. thanks the Spanish MINECO for the financial support through the RyC program. The authors would like to thank the technical staff of the ICMAB for their assistance, We report on magnetotransport properties on La_(0.7)Sr_(0.3)MnO_(3)/MgO/Fe tunnel junctions grown epitaxially on top of (001)-oriented SrTiO_(3) substrates by sputtering. It is shown that the magnetoresistive response depends critically on the MgO/Fe interfacial properties. The appearance of an FeOX layer by the interface destroys the 1 symmetry filtering effect of the MgO/Fe system and only a small negative tunneling magnetoresistance (TMR) (∼ −3 %) is measured. However, in annealed samples a switchover from positive TMR (∼ +25% at 70 K) to negative TMR (∼ −1 %) is observed around 120 K. This change is associated with the transition from semiconducting at high T to insulating at low T taking place at the Verwey transition (TV ∼ 120 K) in Fe3O4, thus suggesting the formation of a very thin slab of magnetite at the MgO/Fe interface during annealing treatments. These results highlight the relevance of interfacial properties on the tunneling conduction process and how it can be substantially modified through appropriate interface engineering., Comunidad de Madrid, Ministerio de Economía y Competitividad (MINECO), Basque Government, FEDER program, Marie Curie Actions, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2011 American Physical Society. Artículo firmado por 13 autores. We acknowledge financial support from MICINN grants MAT2008-06517-C02-01, CSD2009-00013, MAT2008-06517-C02-02, and PI2010-60E013 and provision of beamtime by the European Synchrotron Radiation Facility., We report the observation between 40 and 120 K of anomalous magnetic hysteresis loops in thin epitaxial films of La_(0.7)Ca_(0.3)MnO_(3) grown on ferroelectric BaTiO_(3). These hysteresis loops display extremely unusual features: after switching at coercivity, the magnetization overshoots the eventual high-field value. We study the strains in the film and substrate with x-ray diffraction and propose a model of two magnetic moment populations with different magnetoelastic anisotropies. The relative weights of both populations can be estimated by comparison with twin samples of La_(0.7)Ca_(0.3)MnO_(3) films on nonferroelectric SrTiO_(3). We propose that the observed magnetization overshoots the result from differences in the magnetostriction balance as the applied magnetic field increases. The picture of a nonuniform strain field in La_(0.7)Ca_(0.3)MnO_(3) on BaTiO_(3), caused by the corrugation of the ferroelectric domains in the rhombohedric phase of BaTiO_(3), is compatible with the magnetic granular behavior observed in the temperature and field dependences of the magnetization as well as in the low temperature magnetoresistance exhibited by the epitaxial film., MICINN, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2015 Macmillan Publishers Limited. We acknowledge financial support from the European Research Council (ERC Advanced Grant FEMMES, No. 267579) and the Labex NanoSaclay project FIRET. The ALICE project is supported by the BMBF Contract No. 05K10PC2. The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007–2013) under grant agreement no. 226716. Work at UCM was supported by grants MAT2011-27470-C02 and Consolider Ingenio 2010—CSD2009- 00013 (Imagine), by CAM through grant S2009/MAT-1756 (Phama) and by the ERC starting Investigator Award, grant #239739 STEMOX. Microscopy at ORNL (M.V.) was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division. We thank N.M. Nemes and M. Garcı´a- Herna´ndez for collaboration and assistance with the preliminary magnetic characterization of the LSMO/LFO structures and V. Garcia for his constructive comments. Author contributions: F.Y.B., J.S., A.B. and M.B. designed and conceived the experiment. F.Y.B. and A.R.-C. were involved in sample growth and characterization. F.Y.B. and C.V were involved in lithography process and transport measurements. S.V. conceived the synchrotron experiments. F.Y.B., S.V., R.A., J.T., A.A.U¨ . and A.R.-C. were involved in synchrotron measurements and data analysis. M.V. and S.J.P. performed electron microscopy. M.N.G. and M.B performed tunnelling magneto-resistance simulations. F.Y.B., M.N.G., C.V., Z.S., C.L., J.E.V., J.S., A.B. and M.B analyzed the data and discussed the manuscript. F.Y.B. and M.B. wrote the article with inputs from all co-authors. Competing financial interests: The authors declare no competing financial interests., At interfaces between complex oxides, electronic, orbital and magnetic reconstructions may produce states of matter absent from the materials involved, offering novel possibilities for electronic and spintronic devices. Here we show that magnetic reconstruction has a strong influence on the interfacial spin selectivity, a key parameter controlling spin transport in magnetic tunnel junctions. In epitaxial heterostructures combining layers of antiferromagnetic LaFeO_3 (LFO) and ferromagnetic La_0.7Sr_0.3MnO_3 (LSMO), we find that a net magnetic moment is induced in the first few unit planes of LFO near the interface with LSMO. Using X-ray photoemission electron microscopy, we show that the ferromagnetic domain structure of the manganite electrodes is imprinted into the antiferromagnetic tunnel barrier, endowing it with spin selectivity. Finally, we find that the spin arrangement resulting from coexisting ferromagnetic and antiferromagnetic interactions strongly influences the tunnel magnetoresistance of LSMO/LFO/LSMO junctions through competing spin-polarization and spin-filtering effects., Unión Europea. FP7, Comunidad Autónoma de Madrid, Ministerio de Economía y Competitividad (MINECO), Labex NanoSaclay project FIRET, ALICE Project (BMBF), Bundesministerium für Bildung und Forschung (BMBF), Alemania, European Research Council, Programa Consolider-Ingenio (Imagine), MINECO, España, ERC starting Investigator Award STEMOX, US Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division, PHOTONIC ADVANCED MATERIALS: PHAMA 2.0-CM PROGRAMME, Consejo Superior de Investigaciones Científicas (CSIC), España, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

©2011 American Physical Society. This work was supported by Spanish MICINN Grant No. MAT 2008 06517, Consolider Ingenio Grant No. CSD2009-00013 (IMAGINE), and CAM Grant No. S2009-MAT 1756 (PHAMA)., Metallic surface layers are fabricated by doping (100) SrTiO_3 (STO) single crystals with oxygen vacancies generated by bombardment with Ar ions from an rf plasma source. The presence of oxygen vacancies is confirmed by cathodoluminescence and x-ray photoemission spectroscopy. This technique produces a surface electron gas with high values of the sheet carrier density (n_(2D) = 2.45x10^17 cm^(-2)). A strong increase (300%) of the low-temperature magnetoresistance is observed when the magnetic field is rotated away from the surface, characteristic of orbital effects of confined electrons. We estimate the width of the confinement region to be in the 200-300 nm range. When a magnetic field is applied in the surface plane and parallel to the current direction, a large negative magnetoresistance is found below the structural transition of the STO, which is discussed in terms of spin-orbit scattering. On further reduction of temperature, there is a change to a positive magnetoresistance regime due to the scattering of charge carriers at the disordered surface region., Comunidad de Madrid, Ministerio de Ciencia e Innovación (MICINN), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2016 Author(s). We thank J. Pearson for assistance with SQUID magnetometry study. Work at ORNL is supported by the Division of Scientific User Facilities of the Office of Basic Energy Sciences (BES), US Department of Energy (DOE). Work at MSD, ANL was supported by the U.S. DOE, Office of Science, BES, Materials Sciences and Engineering Division. Research at UCM was supported by Spanish MICINN through Grant Nos. MAT2014-52405-C02-01 and Consolider Ingenio 2010-CSD2009-00013 (Imagine), by CAM through Grant No. S2014/MAT-PHAMA II. This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. We also thank Diamond Light Source for access to beamline I10., 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., Division of Scientific User Facilities of the Office of Basic Energy Sciences (BES), US Department of Energy (DOE), U.S. DOE, Office of Science, BES, Materials Sciences and Engineering Division, Spanish MICINN, Consolider Ingenio 2010, CAM, Argonne National Laboratory, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Generation, manipulation, and sensing of magnetic domain walls are cornerstones in the design of efficient spintronic devices. Half-metals are amenable for this purpose as large low field magnetoresistance signals can be expected from spin accumulation at spin textures. Among half metals, La1−xSrxMnO3 (LSMO) manganites are considered as promising candidates for their robust half-metallic ground state, Curie temperature above room temperature (Tc = 360 K, for x = 1/3), and chemical stability. Yet domain wall magnetoresistance is poorly understood, with large discrepancies in the reported values and conflicting interpretation of experimental data due to the entanglement of various source of magnetoresistance, namely, spin accumulation, anisotropic magnetoresistance, and colossal magnetoresistance. In this work, the domain wall magnetoresistance is measured in LSMO cross-shape nanowires with single-domain walls nucleated across the current path. Magnetoresistance values above 10% are found to be originating at the spin accumulation caused by the mistracking effect of the spin texture of the domain wall by the conduction electrons. Fundamentally, this result shows the importance on non-adiabatic processes at spin textures despite the strong Hund coupling to the localized t2g electrons of the manganite. These large magnetoresistance values are high enough for encoding and reading magnetic bits in future oxide spintronic sensors. © 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.

[EN] The electronic reconstruction occurring at oxide interfaces may be the source of interesting device concepts for future oxide electronics. Among oxide devices, multiferroic tunnel junctions are being actively investigated as they offer the possibility to modulate the junction current by independently controlling the switching of the magnetization of the electrodes and of the ferroelectric polarization of the barrier. In this Letter, we show that the spin reconstruction at the interfaces of a La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 multiferroic tunnel junction is the origin of a spin filtering functionality that can be turned on and off by reversing the ferroelectric polarization. The ferroelectrically controlled interface spin filter enables a giant electrical modulation of the tunneling magnetoresistance between values of 10% and 1000%, which could inspire device concepts in oxides-based low dissipation spintronics.

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.

In this paper, we explore the interfacial effects appearing in highly strained La0.7Ca0.3MnO3 (LCMO) ultra-thin films (10-12nm) grown on BaTiO3 (BTO) ferroelectric substrates. The strong tendency to phase separation of this optimally doped manganite contributes to the exotic phenomena observed in magnetism and transport experiments: the so-called Matteucci magnetic loops, magnetic granularity and a second metal insulator transition are observed between 50K and the LCMO Curie temperature, 180K. All these properties define the multiferroic character of these heterostructures, which in LCMO//BTO system is strongly linked to magnetoelastic coupling.