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Cabero Piris, Mariona

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Mariona

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Cabero Piris

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Universidad Complutense de Madrid

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Ferroelectric control of interface spin filtering in multiferroic tunnel junctions
(American Physical Society, 2019-01-22) Tornos Castillo, Javier; Gallego Toledo, Fernando; Hernández Martín, David; Orfila Rodríguez, Gloria; Cabero Piris, Mariona; Cuéllar Jiménez, Fabián Andrés; Arias Serna, Diego; Rivera Calzada, Alberto Carlos; Sefriuoi, Zouhair; León Yebra, Carlos; Santamaría Sánchez-Barriga, Jacobo
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.
Fenómenos interfacionales asociados a vacantes de oxígeno en heteroestructuras de óxidos
(Universidad Complutense de Madrid, 2018-05-18) Cabero Piris, Mariona; Santamaría Sánchez-Barriga, Jacobo
Los óxidos complejos son una familia de compuestos de óxidos de metales de transición con un amplio espectro de propiedades para su aplicación en electrónica de óxidos, como son: ferromagnetismo, antiferromagnetismo, superconductividad, ferroelectricidad, etc. En particular, son buenos candidatos para dispositivos reales, ya que las interfases de estos materiales generan un escenario prometedor gracias a la interacción entre sus efectos eléctricos y magnéticos [1]. Las distintas interacciones entre los distintos grados de libertad como son la carga, el espín, la red cristalina y los orbitales dan lugar a una amplia variedad de fases electrónicas. Por tanto, la combinación de estas propiedades en heteroestructuras de alta calidad cristalina pueden dar lugar a diferentes estados electrónicos [2]. El comportamiento de los electrones en estos sistemas está sujeto a las interacciones culombianas con primeros vecinos y, por tanto, los materiales no se pueden describir con el modelo clásico de bandas. Un ejemplo de este tipo de comportamiento es el que se da en los aislantes de Mott, en los que la repulsión culombiana es suficientemente intensa para inducir un estado aislante a pesar de que la teoría de bandas prediga exactamente lo opuesto para una ocupación parcial de las bandas [3]. Es bien sabido que este tipo de materiales crecen con deficiencias de oxígeno, las cuales pueden dar lugar a cambios en sus las propiedades físicas, ya sea por el efecto electrónico de dopado o por los cambios estructurales que puedan generar en la red cristalina. Por ejemplo, el LaMnO3 estequiometrico es un aislante antiferromagnético que presenta ferromagnetismo cuando la red es deficiente en oxígeno [4]. Otros estudios demuestran que la familia de cobaltitas (La,Sr)CoO3 en película delgada sobre sustratos de NdGaO3 y (La,Sr)(Al,Ta)O3 tiene diferentes imanaciones de saturación [5]. Es estos experimentos se ha demostrado que, la diferencia en el contenido de vacantes de oxígeno en las películas delgadas para diferentes sustratos pueden ser responsables de la mejora observada en las propiedades magnéticas. Un caso particularmente importante es el del LaCoO3, en el que se ha demostrado que cuando se crece en película delgada hay que tener en cuenta la combinación de la tensión epitaxial y las vacantes de oxígeno, pues ambos fenómenos son interdependientes. En este caso, la estabilización de espín del Co2+ y Co3+ está directamente relacionado con una superestructura ordenada de vacantes en la red que da lugar a la interacción de canje ferromagnética...
Graphite to diamond transition induced by photoelectric absorption of ultraviolet photons
(Nature publishing group, 2021-01-28) Gómez de Castro, Ana Inés; Rheinstadter, Maikel; Clancy, Patrick; Castilla, Maribel; Isidro, Federico de; Larruquert, Juan, I; De Lis-Sanchez, Tomás; Britten, James; Cabero Piris, Mariona; Isidro Gómez, Federico P. de
The phase transition from graphite to diamond is an appealing object of study because of many fundamental and also, practical reasons. The out-of-plane distortions required for the transition are a good tool to understand the collective behaviour of layered materials (graphene, graphite) and the van der Waals forces. As today, two basic processes have been successfully tested to drive this transition: strong shocks and high energy femtolaser excitation. They induce it by increasing either pressure or temperature on graphite. In this work, we report a third method consisting in the irradiation of graphite with ultraviolet photons of energies above 4.4 eV. We show high resolution electron microscopy images of pyrolytic carbon evidencing the dislocation of the superficial graphitic layers after irradiation and the formation of crystallite islands within them. Electron energy loss spectroscopy of the islands show that the sp(2) to sp(3) hybridation transition is a surface effect. High sensitivity X-ray diffraction experiments and Raman spectroscopy confirm the formation of diamond within the islands.
A combined micro-Raman, X-ray absorption and magnetic study to follow the glycerol-assisted growth of epsilon-iron oxide sol-gel coatings
(Elsevier Science SA, 2022-02-05) López Sánchez, Jesús; Serrano, Aída; Campo, A. del; Muñoz Noval, Álvaro; Salas Colera, Eduardo; Cabero Piris, Mariona; Varela del Arco, María; Abuín, Manuel; Castro, German R.; Rubio Zuazo, Juan; Rodríguez de la Fuente, Óscar; Carmona Tejero, Noemí
Epsilon iron oxide (epsilon-Fe_2O_3) coatings on Si(100) substrates are obtained by an easy one-pot sol-gel recipe assisted by glycerol in an acid medium. Glycerol, given its small dimensions, enables the formation of epsilon-Fe_2O_3 nanoparticles with a size of a few nanometers and the highest purity is reached in coatings after a densification treatment at 960 degrees C. The structural and compositional evolution up to 1200 degrees C is studied by confocal Raman microscopy and X-ray absorption spectroscopy techniques, correlating the existing magnetic properties. We report a novel characterization method, which allows monitoring the evolution of the precursor micelles as well as the intermediate and final phases formed. Furthermore, the inherent industrial technology transfer of the sol-gel process is also demonstrated with the epsilon-Fe_2O_3 polymorph, impelling its application in the coatings form.
Ferroionic inversion of spin polarization in a spin-memristor
(American Institute of Physics, 2021-03-01) Rouco Gómez, Víctor; Gallego Toledo, Fernando; Hernández Martín, D.; Sánchez Manzano, David; Tornos Castillo, Javier; Beltrán Finez, Juan Ignacio; Cabero Piris, Mariona; Cuéllar Jiménez, Fabián Andrés; Arias Serna, Diego; Sánchez Santolino, Gabriel; Mompean, F. J.; García Hernández, M.; Rivera Calzada, Alberto Carlos; Varela del Arco, María; Muñoz, M. C.; León Yebra, Carlos; Sefrioui, Zouhair; Santamaría Sánchez-Barriga, Jacobo
Magnetoelectric coupling in artificial multiferroic interfaces can be drastically affected by the switching of oxygen vacancies and by the inversion of the ferroelectric polarization. Disentangling both effects is of major importance toward exploiting these effects in practical spintronic or spinorbitronic devices. We report on the independent control of ferroelectric and oxygen vacancy switching in multiferroic tunnel junctions with a La_(0.7)Sr_(0.3)MnO_3 bottom electrode, a BaTiO_3 ferroelectric barrier, and a Ni top electrode. We show that the concurrence of interface oxidation and ferroelectric switching allows for the controlled inversion of the interface spin polarization. Moreover, we show the possibility of a spin-memristor where the controlled oxidation of the interface allows for a continuum of memresistance states in the tunneling magnetoresistance. These results signal interesting new avenues toward neuromorphic devices where, as in practical neurons, the electronic response is controlled by electrochemical degrees of freedom.
Controlled sign reversal of electroresistance in oxide tunnel junctions by electrochemical-ferroelectric coupling
(American Physical Society, 2020-12-30) Hernández Martín, David; Gallego Toledo, Fernando; Tornos Castillo, Javier; Rouco Gómez, Víctor; Beltrán Finez, Juan Ignacio; Munuera, C.; Sánchez Manzano, David; Cabero Piris, Mariona; Cuéllar Jiménez, Fabián Andrés; Arias Serna, Diego; Sánchez Santolino, Gabriel; Mompean, F. J.; García Hernández, M.; Rivera Calzada, Alberto Carlos; Pennycook, S. J.; Varela del Arco, María; Muñoz, M. C.; Sefrioui, Zouhair; León Yebra, Carlos; Santamaría Sánchez-Barriga, Jacobo
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.
Yttria-stabilized zirconia/SrTiO_(3) oxide heteroepitaxial interface with symmetry discontinuity
(Amer Inst Physics, 2014-06-23) Scigaj, M.; Dix, N.; Cabero Piris, Mariona; Rivera Calzada, Alberto Carlos; Santamaría Sánchez-Barriga, Jacobo; Fontcuberta, J.
We show that yttria-stabilized zirconia (YSZ) films deposited on structurally dissimilar SrTiO_(3)(110) substrates exhibit two-dimensional layer-by-layer growth. We observed that, up to a thickness of about 15 nm, the square (001) basal plane of the cubic YSZ grows epitaxially on the rectangular (110) crystallographic plane of SrTiO3 substrates, with [110]YSZ(001)//[001]SrTiO_(3)(110) epitaxial relationship. Thus, the heterointerface presents symmetry discontinuity between the YSZ(001) film and the lower surface symmetry SrTiO_(3)(110) substrate. Beyond this specific case, we envisage similar approaches to develop other innovative oxide interfaces showing similar crystal symmetry discontinuities.
Modified magnetic anisotropy at LaCoO_(3)/La_(0.7)Sr_(0.3)MnO_(3) interfaces
(American Institute of Physics, 2017-09) Cabero Piris, Mariona; Nagy, K.; Gallego, F.; Sander, A.; Rio, M.; Cuéllar Jiménez, Fabián Andrés; Tornos, J.; Hernández Martín, David; Nemes, Norbert Marcel; Mompean, F.; García Hernández, M.; Rivera Calzada, Alberto Carlos; Sefrioui, Zouhair; Reyren, N.; Feher, T.; Varela del Arco, María; León Yebra, Carlos; Santamaría Sánchez-Barriga, Jacobo
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 La0.7Sr0.3MnO3 (LSMO) with an ultrathin LaCoO3 (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.
Large intrinsic anomalous Hall effect in SrIrO_3 induced by magnetic proximity effect
(Nature Publishing Group, 2021-06-02) Tornos Castillo, Javier; Peralta Somoza, Andrea; Sánchez Manzano, David; Gallego Toledo, Fernando; Cabero Piris, Mariona; Sánchez Santolino, Gabriel; González Calbet, José María; Rivera Calzada, Alberto Carlos; León Yebra, Carlos; Santamaría Sánchez-Barriga, Jacobo; ..., otros
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.
Unraveling dzyaloshinskii-moriya interaction and chiral nature of graphene/cobalt interface
(Amer Chemical Soc, 2018-09) Cabero Piris, Mariona; Varela del Arco, María
A major challenge for future spintronics is to develop suitable spin transport channels with long spin lifetime and propagation length. Graphene can meet these requirements, even at room temperature. On the other side, taking advantage of the fast motion of chiral textures, that is, Neel-type domain walls and magnetic skyrmions, can satisfy the demands for high- density data storage, low power consumption, and high processing speed. We have engineered epitaxial structures where an epitaxial ferromagnetic Co layer is sandwiched between an epitaxial Pt(111) buffer grown in turn onto MgO(111) substrates and a grapheme layer. We provide evidence of a graphene-induced enhancement of the perpendicular magnetic anisotropy up to 4 nm thick Co films and of the existence of chiral left-handed Neel-type domain walls stabilized by the effective Dzyaloshinskii-Moriya interaction (DMI) in the stack. The experiments show evidence of a sizable DMI at the gr/Co interface, which is described in terms of a conduction electron mediated Rashba-DMI mechanism and points opposite to the spin orbit coupling-induced DMI at the Co/Pt interface. In addition, the presence of graphene results in (i) a surfactant action for the Co growth, producing an intercalated, flat, highly perfect face-centered cubic film, pseudomorphic with Pt and (ii) an efficient protection from oxidation. The magnetic chiral texture is stable at room temperature and grown on insulating substrate. Our findings open new routes to control chiral spin structures using interfacial engineering in graphene-based systems for future spin- orbitronics devices fully integrated on oxide substrates.