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© 2011 American Physical Society. Este artículo está firmado por 13 autores. Work at UCM was supported by Spanish MICINN Grant No. MAT 2008 06517, Consolider Ingenio CSD2009- 00013 (IMAGINE), and CAM S2009-MAT 1756 (PHAMA). Work at ORNL was supported by the Materials Sciences and Engineering Division, Office of Basic Energy Sciences, U.S. Department of Energy. M. V. acknowledges ERC starting Grant No. 239739 STEMOX., We report on the magnetic coupling of La_(0.7)Sr_(0.3)MnO_(3) layers through SrTiO_(3) spacers in La_(0.7)Sr_(0.3)MnO_(3)/SrTiO_(3) epitaxial heterostructures. Combined aberration-corrected microscopy and electron-energy-loss spectroscopy evidence charge transfer to the empty conduction band of the titanate. Ti d electrons interact via superexchange with Mn, giving rise to a Ti magnetic moment as demonstrated by x-ray magnetic circular dichroism. This induced magnetic moment in the SrTiO_(3) controls the bulk magnetic and transport properties of the superlattices when the titanate layer thickness is below 1 nm., Spanish MICINN, CAM, Materials Sciences and Engineering Division, Office of Basic Energy Sciences, U.S. Department of Energy, ERC, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

We report on the magnetic coupling of La0.7Sr0.3MnO3 layers through SrTiO3 spacers in La0.7Sr0.3MnO3/SrTiO3 epitaxial heterostructures. Combined aberration-corrected microscopy and electron-energy-loss spectroscopy evidence charge transfer to the empty conduction band of the titanate. Ti d electrons interact via superexchange with Mn, giving rise to a Ti magnetic moment as demonstrated by x-ray magnetic circular dichroism. This induced magnetic moment in the SrTiO3 controls the bulk magnetic and transport properties of the superlattices when the titanate layer thickness is below 1 nm., MICINN, CAM, U.S. Department of Energy, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2002 The American Physical Society., Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2010 The American Physical Society. We acknowledge financial support by Junta de Comunidades de Castilla-La Mancha through Project No. PAI-05- 013, by CAM under Grant No. S2009/MAT-1756 Phama, by Spanish MICINN through Grants No. MAT2008-06517- C02, No. MAT2008-06542-C04, and No. FIS2009-12964- C05-04, and Consolider Ingenio 2010 under Grant No. CSD2009-00013 Imagine. We thank J. Garcia-Barriocanal for helpful discussions. We are indebted to the staff of SpLine for their help during the experimental work at ESRF., We report on the effect of grain size on the ionic conductivity of yttria-stabilized zirconia samples synthesized by ball milling. Complex impedance measurements, as a function of temperature and frequency are performed on 10 mol % yttria-stabilized zirconia nanocrystalline samples with grain sizes ranging from 900 to 17 nm. Bulk ionic conductivity decreases dramatically for grain sizes below 100 nm, although its activation energy is essentially independent of grain size. The results are interpreted in terms of a space-charge layer resulting from segregation of mobile oxygen vacancies to the grain-boundary core. The thickness of this space-charge layer formed at the grain boundaries is on the order of 1 nm for large micron-sized grains but extends up to 7 nm when decreasing the grain size down to 17 nm. This gives rise to oxygen vacancies depletion over a large volume fraction of the grain and consequently to a significant decrease in oxide-ion conductivity., Junta de Comunidades de Castilla-La Mancha, CAM, Spanish MICINN, Consolider Ingenio 2010, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

The local order around Zr and Y atoms of nanocrystalline yttria-stabilized zirconia (YSZ) powders with different grain sizes has been investigated by x-ray absorption spectroscopies. The samples were prepared by means of mechanical alloying with or without subsequent sintering treatment and also by milling commercial YSZ. Our study is motivated by the interest in the electrical properties of grain boundaries and the controversy about the level of disorder in the intergrain regions in nanocrystalline YSZ. The x-ray absorption near edge structure (XANES) analysis indicates that the local order of all the sintered samples is independent of the grain size. This is confirmed by the analysis of the extended x-ray absorption fine structure, which points out also that, in contrast to that found in sintered samples, the local order around the cation in the samples milled without further sintering treatment extends only to the first coordination shell. Finally, the results of ab initio Zr K-edge XANES calculations lead us to conclude that the observed changes of the shape of the white line are not related to a phase transformation but reflects the short-range order present in the as-milled samples., Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2023 American Physical Society The synthesis of the heterostructures and measurement of transport, magnetic, and optical properties were supported by the U.S. Department of Energy's Office of Basic Energy Science, under Grant DE-FG02-87ER45332, the synthesis of LSMO by the Spanish MCI through Grants No. MAT 2017-87134-C02 and No. PCI 2020-112093, and theory by the French ANR "MoMA" project ANR-19-CE30-0020, Chilean FONDECYT 1211902, and Basal AFB220001., The strongly correlated material La_0.7Sr_0.3MnO_3 (LSMO) exhibits metal-to-insulator and magnetic tran-sition near room temperature. Although the physical properties of LSMO can be manipulated by strain, chemical doping, temperature, or magnetic field, they often require large external stimuli. To include addi-tional flexibility and tunability, we developed a hybrid optoelectronic heterostructure that uses photocarrier injection from cadmium sulfide (CdS) to an LSMO layer to change its electrical conductivity. LSMO exhibits no significant optical response; however, the CdS/LSMO heterostructures show an enhanced conductivity, with a resistance drop of about 37%, at the transition temperature under light stimuli. This enhanced conductivity in response to light is comparable to the effect of a 9 T magnetic field in pure LSMO. Surprisingly, the optical and magnetic responses of CdS/LSMO heterostructures are decoupled and exhibit different effects when both stimuli are applied. This unexpected behavior shows that het-erostructuring strongly correlated oxides may require a new understanding of the coupling of physical properties across the transitions and provide the means to implement new functionalities., U.S. Department of Energy's Office of Basic Energy Science, Ministerio de Ciencia e Innovación (MICINN), Agence nationale de la recherche (ANR), Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2004 The American Physical Society. C.L. and A.R. thank J. Santamaría for fruitful discussions. Financial support from CICYT Grant No. MAT2001-3713- C04 is acknowledged. The work performed at NRL was supported by ONR., For ionic conductivity relaxation in ionically conducting materials we predict in the framework of the coupling model that the magnitude of the ubiquitous near constant loss correlates with the activation energy E_(a) for independent ion hopping. Using experimental data of a variety of ionic conductors, this correlation has been borne out. The model also explains the observed correlation between the magnitude of the near constant loss and the value of the dc conductivity at room temperature, as well as the temperature dependence for the near constant loss., CICYT, ONR, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2019 American Physical Society Artículo firmado por más de once autores. Authors acknowledge received funding from the project Quantox of QuantERA ERA-NET Cofund in Quantum Technologies (Grant Agreement No. 731473) implemented within the European Union's Horizon 2020 Programme. This work was supported by Spanish MINECO through Grants No. MAT2014-52405-C02, No. MAT2017-87134-C02, No. MAT2015-72795-EXP, and by Comunidad de Madrid through S2013/336 MIT-2740. Work at Argonne National Laboratory (PNR experiments and analysis) was supported by the U.S. DOE, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. The neutron scattering experiment was conducted at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. Beam time support provided at Alice (BMBF Project No. 05K10PC2) is acknowledged. Financial support for developing and building the PM2-VEKMAG beam line and VEKMAG end station was provided by HZB and BMBF (05K10PC2, 05K10WR1, 05K10KE1), respectively. Steffen Rudorff is acknowledged for technical support. J. S. thanks Scholarship program Alembert funded by the IDEX Paris-Saclay, ANR-11-IDEX-0003-02., 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 La_0.7Sr_0.3MnO_3/BaTiO_3/La_0.7Sr_0.3MnO_3 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., Union Europea. H2020, Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid, Bundesministerium für Bildung und Forschung (BMBF), Université Paris-Saclay, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

[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.

The authors acknowledge received funding from the project Quantox of QuantERA ERA-NET Cofund in Quantum Technologies (Grant Agreement No. 731473) implemented within the European Union's Horizon 2020 Programme. Work supported by Spanish MINECO through Grants No. MAT2014-52405-C02, No. MAT2017-87134-C02, No. MAT2015-066888-C3-1-3-R, and No. RTI2018-097895-B-C41 (-C43), Grant No. Santander-UCM PR87/19-22603, and computational support from Grant No. FI-2019-1-0012. J. S. thanks for the scholarship program Alembert funded by the IDEX Paris-Saclay, Grant No. ANR-11-IDEX-0003-02., 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 nanometerthick 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 La_0.7Sr_0.3MnO_3 bottom electrode and 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 neuromorphie computing., Unión Europea, Ministerio de Economía, Comercio y Empresa (España), Ministerio de Ciencia, Innovación y Universidades (España), Universidad Complutense de Madrid/Banco de Santander, Universidad París-Saclay/ IDEX, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub