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102. Magnetotransport in MgO-based magnetic tunnel junctions grown by molecular beam epitaxy (invited).

Author

Andrieu, S., Bonell, F., Hauet, T., Montaigne, F., Calmels, L., Snoeck, E., Lefevre, P., and Bertran, F.

Subjects
CRYSTAL growth, ELECTRIC resistors, NANOTECHNOLOGY, PARTICLES (Nuclear physics), ELECTRON emission
Abstract

The strong impact of molecular beam epitaxy growth and Synchrotron Radiation characterization tools in the understanding of fundamental issues in nanomagnetism and spintronics is illustrated through the example of fully epitaxial MgO-based Magnetic Tunnel Junctions (MTJs). If ab initio calculations predict very high tunnel magnetoresistance (TMR) in such devices, some discrepancy between theory and experiments still exists. The influence of imperfections in real systems has thus to be considered like surface contaminations, structural defects, unexpected electronic states, etc. The influence of possible oxygen contamination at the Fe/MgO(001) interface is thus studied, and is shown to be not so detrimental to TMR as predicted by ab initio calculations. On the contrary, the decrease of dislocations density in the MgO barrier of MTJs using Fe1-xVx electrodes is shown to significantly increase TMR. Finally, unexpected transport properties in Fe1-XCox/MgO/ Fe1-XCox (001) are presented. With the help of spin and symmetry resolved photoemission and ab initio calculation, the TMR decrease for Co content higher than 25% is shown to come from the existence of an interface state and the shift of the empty D1 minority spin state towards the Fermi level. [ABSTRACT FROM AUTHOR]

Published
2014
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105. Epitaxial cobalt-based Heusler alloys for spintronic applications: Elaboration, structural and magnetic investigation

Author

Guillemard, C., Bertran, F., Bataille, A., Le Fevre, P., Petit-Watelot, S., Rojas-Sánchez, J.-C., Andrieu, Stéphane, Institut Jean Lamour (IJL), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), LLB - Nouvelles frontières dans les matériaux quantiques (NFMQ), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Tohoku University

Subjects
[PHYS]Physics [physics]
Abstract

International audience

Published
2017

106. Two-dimensional electron systems in ATiO3 perovskites (A=Ca, Ba, Sr): Control of orbital hybridization and energy order

Author

Rödel, T. C., Vivek, M., Fortuna, F., Le Fèvre, P., Bertran, F., Weht, Ruben Oscar, Goniakowski, J., Gabay, M., and Santander Syro, A. F.

Subjects
Astronomía, purl.org/becyt/ford/1 [https], Ciencias Físicas, Superficies, Propiedades Electrónicas, purl.org/becyt/ford/1.3 [https], CIENCIAS NATURALES Y EXACTAS
Abstract

We report the existence of a two-dimensional electron system (2DES) at the (001) surface of CaTiO3. Using angle-resolved photoemission spectroscopy, we find a hybridization between the dxz and dyz orbitals, not observed in the 2DESs at the surfaces of other ATiO3 perovskites, e.g., SrTiO3 or BaTiO3. Based on a comparison of the 2DES properties in these three materials, we show how the electronic structure of the 2DES (bandwidth, orbital energy order, and electron density) is coupled to different typical lattice distortions in perovskites. The orbital hybridization in orthorhombic CaTiO3 results from the rotation of the oxygen octahedra, which can also occur at the interface of oxide heterostructures to compensate strain. More generally, the control of the orbital energy order in 2DES by choosing different A-site cations in perovskites offers a gateway toward 2DESs in oxide heterostructures beyond SrTiO3. Fil: Rödel, T. C.. Université Paris Sud; Francia. Synchrotron SOLEIL; Francia Fil: Vivek, M.. Université Paris Sud; Francia. Centre National de la Recherche Scientifique; Francia Fil: Fortuna, F.. Université Paris Sud; Francia Fil: Le Fèvre, P.. Synchrotron SOLEIL; Francia Fil: Bertran, F.. Synchrotron SOLEIL; Francia Fil: Weht, Ruben Oscar. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Goniakowski, J.. Universite de Paris VI. Institut des Nanosciences de Paris; Francia Fil: Gabay, M.. Université Paris Sud; Francia. Centre National de la Recherche Scientifique; Francia Fil: Santander Syro, A. F.. Université Paris Sud; Francia

Published
2017

107. Spin-resolved electronic structure of ferroelectric ��-GeTe and multiferroic Ge1-xMnxTe

Author

Krempasky, J., Fanciulli, M., Min��r, J., Khan, W., Muntwiler, M., Bertran, F., Muff, S., Weber, A. P., Strocov, V. N., Volobuiev, V. V., Springholz, G., and Dil, J. H.

Subjects
Condensed Matter::Materials Science, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, Condensed Matter::Strongly Correlated Electrons
Abstract

Germanium telluride features special spin-electric effects originating from spin-orbit coupling and symmetry breaking by the ferroelectric lattice polarization, which opens up many prospectives for electrically tunable and switchable spin electronic devices. By Mn doping of the ��-GeTe host lattice, the system becomes a multiferroic semiconductor possessing magnetoelectric properties in which the electric polarization, magnetization and spin texture are coupled to each other. Employing spin- and angle-resolved photoemission spectroscopy in bulk- and surface-sensitive energy ranges and by varying dipole transition matrix elements, we disentangle the bulk, surface and surface-resonance states of the electronic structure and determine the spin textures for selected parameters. From our results, we derive a comprehensive model of the ��-GeTe surface electronic structure which fits experimental data and first principle theoretical predictions and we discuss the unconventional evolution of the Rashba-type spin splitting upon manipulation by external B- and E-fields., 7 pages, 7 figures, 1 ancillary file

Published
2017
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108. Two-dimensional electron systems in $A{\mathrm{TiO}}_{3}$ perovskites ($A=\mathrm{Ca}$, Ba, Sr): Control of orbital hybridization and energy order

Author

Rödel, T.C., Vivek, M., Fortuna, F., Le Fèvre, P., Bertran, F., Weht, R., Goniakowski, J., Gabay, M., Santander-Syro, A.F., Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Solides (LPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Institut des Nanosciences de Paris (INSP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), and Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)

Subjects
[PHYS]Physics [physics]
Abstract

International audience; We report the existence of a two-dimensional electron system (2DES) at the ( 001 ) surface of CaTiO 3 . Using angle-resolved photoemission spectroscopy, we find a hybridization between the d x z and d y z orbitals, not observed in the 2DESs at the surfaces of other A TiO 3 perovskites, e.g., SrTiO 3 or BaTiO 3 . Based on a comparison of the 2DES properties in these three materials, we show how the electronic structure of the 2DES (bandwidth, orbital energy order, and electron density) is coupled to different typical lattice distortions in perovskites. The orbital hybridization in orthorhombic CaTiO 3 results from the rotation of the oxygen octahedra, which can also occur at the interface of oxide heterostructures to compensate strain. More generally, the control of the orbital energy order in 2DES by choosing different A -site cations in perovskites offers a gateway toward 2DESs in oxide heterostructures beyond SrTiO 3 .

Published
2017

109. Co/Ni multilayers for spintronics: High spin polarization and tunable magnetic anisotropy

Author

Andrieu, S., primary, Hauet, T., additional, Gottwald, M., additional, Rajanikanth, A., additional, Calmels, L., additional, Bataille, A. M., additional, Montaigne, F., additional, Mangin, S., additional, Otero, E., additional, Ohresser, P., additional, Le Fèvre, P., additional, Bertran, F., additional, Resta, A., additional, Vlad, A., additional, Coati, A., additional, and Garreau, Y., additional

Published
2018
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110. Cu Metal/Mn Phthalocyanine Organic Spinterfaces atop Co with High Spin Polarization at Room Temperature

Author

Urbain, E., primary, Ibrahim, F., additional, Studniarek, M., additional, Nyakam, F. Ngassam, additional, Joly, L., additional, Arabski, J., additional, Scheurer, F., additional, Bertran, F., additional, Le Fèvre, P., additional, Garreau, G., additional, Denys, E., additional, Wetzel, P., additional, Alouani, M., additional, Beaurepaire, E., additional, Boukari, S., additional, Bowen, M., additional, and Weber, W., additional

Published
2018
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111. High-density two-dimensional electron system induced by oxygen vacancies in ZnO

Author

Rödel, T. C., primary, Dai, J., additional, Fortuna, F., additional, Frantzeskakis, E., additional, Le Fèvre, P., additional, Bertran, F., additional, Kobayashi, M., additional, Yukawa, R., additional, Mitsuhashi, T., additional, Kitamura, M., additional, Horiba, K., additional, Kumigashira, H., additional, and Santander-Syro, A. F., additional

Published
2018
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113. Converting topological insulators into topological metals within the tetradymite family

Author

Chen, K.-W., primary, Aryal, N., additional, Dai, J., additional, Graf, D., additional, Zhang, S., additional, Das, S., additional, Le Fèvre, P., additional, Bertran, F., additional, Yukawa, R., additional, Horiba, K., additional, Kumigashira, H., additional, Frantzeskakis, E., additional, Fortuna, F., additional, Balicas, L., additional, Santander-Syro, A. F., additional, Manousakis, E., additional, and Baumbach, R. E., additional

Published
2018
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119. Surface state of the dual topological insulator Bi(0.9)1Sb(0.09)(11(2)over-bar)

Author

Matsuda, I., Yaji, K., Taskin, A. A., D'angelo, M., Yukawa, R., Ohtsubo, Y., Le Fevre, P., Bertran, F., Yoshizawa, S., Taleb-Ibrahimi, A., Kakizaki, A., Ando, Yoichi, Komori, F., Matsuda, I., Yaji, K., Taskin, A. A., D'angelo, M., Yukawa, R., Ohtsubo, Y., Le Fevre, P., Bertran, F., Yoshizawa, S., Taleb-Ibrahimi, A., Kakizaki, A., Ando, Yoichi, and Komori, F.

Abstract

The electronic structure of a Bi(0.9)1Sb(0.09) single crystal was elucidated at a bisectrix (11 (2) over bar) surface by angle-resolved photoemission spectroscopy using microbeam synchrotron radiation. A Dirac-cone-like dispersion of the surface state was observed at the G (Gamma) over bar point. The detected surface-state band likely corresponds to the one observed in previous quantum transport research (Taskin and Ando, 2009) [14].

Published
2017

120. With emphasis on roman catholic secondary schools in Kumbo diocese, how are the values or morality, good behavior and holistic developments promoted through pedagogies and management in schools

Author

Yuveyonge, Bertran F.

Subjects
education, Kumbo, Roman Catholic Secondary Schools, diakoni, church, studentarbeider, schools, diakonia
Abstract

The church as one of its goals is to foster education. Education remains critically important in the formation of the human person. The research is based primary to answer the following question With emphasis on Roman Catholic Secondary Schools in Kumbo diocese, how are the values of morality, good behavior and holistic developments promoted through pedagogies and management in schools?

Published
2016

121. On the quality of molecular-beam epitaxy grown Fe/MgO and Co/MgO(001) interfaces

Author

Sicot, M., Andrieu, S., Tiusan, C., Montaigne, F., and Bertran, F.

Subjects
Iron compounds -- Structure, Iron compounds -- Chemical properties, Iron compounds -- Magnetic properties, Magnesium oxide -- Structure, Magnesium oxide -- Chemical properties, Magnesium oxide -- Magnetic properties, Physics
Abstract

The structural, chemical, and magnetic properties of Fe at the interface with MgO are investigated. Results state that pollution at the bottom Fe/MgO interface modify drastically spin-dependent tunneling properties.

Published
2006

123. Spin-polarized quasi-one-dimensional state with finite band gap on the Bi/InSb(001) surface

Author

Kishi, J., primary, Ohtsubo, Y., additional, Nakamura, T., additional, Yaji, K., additional, Harasawa, A., additional, Komori, F., additional, Shin, S., additional, Rault, J. E., additional, Le Fèvre, P., additional, Bertran, F., additional, Taleb-Ibrahimi, A., additional, Nurmamat, M., additional, Yamane, H., additional, Ideta, S., additional, Tanaka, K., additional, and Kimura, S., additional

Published
2017
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126. Hubbard band versus oxygen vacancy states in the correlated electron metal SrVO3

Author

Backes, S., primary, Rödel, T. C., additional, Fortuna, F., additional, Frantzeskakis, E., additional, Le Fèvre, P., additional, Bertran, F., additional, Kobayashi, M., additional, Yukawa, R., additional, Mitsuhashi, T., additional, Kitamura, M., additional, Horiba, K., additional, Kumigashira, H., additional, Saint-Martin, R., additional, Fouchet, A., additional, Berini, B., additional, Dumont, Y., additional, Kim, A. J., additional, Lechermann, F., additional, Jeschke, H. O., additional, Rozenberg, M. J., additional, Valentí, R., additional, and Santander-Syro, A. F., additional

Published
2016
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127. Ultrafast filling of an electronic pseudogap in photoexcited (LaS) 1.196 VS 2

Author

Brouet, V, Mauchain, Julien, Papalazarou, E, Faure, Jérôme, Marsi, M, Taleb-Ibrahimi, A, Le Fèvre, P, BERTRAN, F, Cario, Laurent, Janod, Etienne, Corraze, Benoît, Ta Phuoc, V, Perfetti, L, Laboratoire de Physique des Solides (LPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'optique appliquée (LOA), École Nationale Supérieure de Techniques Avancées (ENSTA Paris)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), CASSIOPEE, Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut des Matériaux Jean Rouxel (IMN), Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Ecole Polytechnique de l'Université de Nantes (EPUN), Université de Nantes (UN)-Université de Nantes (UN)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), GREMAN (matériaux, microélectronique, acoustique et nanotechnologies) (GREMAN - UMR 7347), Université de Tours (UT)-Institut National des Sciences Appliquées - Centre Val de Loire (INSA CVL), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Solides Irradiés (LSI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Université de Nantes (UN)-Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Ecole Polytechnique de l'Université de Nantes (EPUN), Université de Nantes (UN)-Université de Nantes (UN), Institut National des Sciences Appliquées - Centre Val de Loire (INSA CVL), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Tours-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), and Faure, Jérôme

Subjects
[PHYS]Physics [physics], Condensed Matter::Strongly Correlated Electrons, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], [PHYS.COND] Physics [physics]/Condensed Matter [cond-mat], [PHYS] Physics [physics]
Abstract

We investigate by angle and time resolved photoemission spectroscopy the unusual insulating state of strongly distorted triangular V slabs in (LaS)1.196VS2. We show that the electronic structure is dominated by the lowest band of the V t2g manifold, which disperses over 0.7 eV and is nearly filled. Hence, (LaS)1.196VS2 is not a Mott insulator. The spectra are strongly temperature dependent, shifting by 100 meV upon cooling to 50 K. The sudden photoexcitation at 50K induces a partial filling of the electronic pseudogap within less than 80 fs. The electronic energy flows into the lattice modes on a comparable timescale. We conclude that a very strong electron-phonon coupling makes this state extremely sensitive to small perturbations of the V clusters distortions.

Published
2015

128. Spin-pumping into surface states of topological insulator ��-Sn, spin to charge conversion at room temperature

Author

Rojas-S��nchez, J. -C., Oyarzun, S., Fu, Y., Marty, A., Vergnaud, C., Gambarelli, S., Vila, L., Jamet, M., Ohtsubo, Y., Taleb-Ibrahimi, A., F��vre, P. Le, Bertran, F., Reyren, N., George, J. -M., and Fert, A.

Subjects
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), FOS: Physical sciences, Condensed Matter::Strongly Correlated Electrons
Abstract

We present experimental results on the conversion of a spin current into a charge current by spin pumping into the Dirac cone with helical spin polarization of the elemental topological insulator (TI) ��-Sn[1-3]. By angle-resolved photoelectron spectroscopy (ARPES) we first confirm that the Dirac cone at the surface of ��-Sn (0 0 1) layers subsists after covering with Ag. Then we show that resonant spin pumping at room temperature from Fe through Ag into ��-Sn layers induces a lateral charge current that can be ascribed to the Inverse Edelstein Effect[4-5]. Our observation of an Inverse Edelstein Effect length[5-6] much longer than for Rashba interfaces[5-10] demonstrates the potential of the TI for conversion between spin and charge in spintronic devices. By comparing our results with data on the relaxation time of TI free surface states from time-resolved ARPES, we can anticipate the ultimate potential of TI for spin to charge conversion and the conditions to reach it., 14 pages, 5 figures

Published
2015
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129. k dependence of the spin polarization in Mn5Ge3/Ge(111) thin films

Author

Ndiaye, W., Mariot, J. -M., De Padova, P., Richter, M. C., Wang, W., Heckmann, O., Taleb-Ibrahimi, A., Le Fevre, P., Bertran, F., Cacho, C., Leandersson, M., Balasubramanian, T., Stroppa, A., Picozzi, S., and Hricovini, K.

Subjects
thin film spin polarization
Abstract

Mn5Ge3(001) thin films grown on Ge(111) were studied by angle-and spin-resolved photoemission using synchrotron radiation in the 17-40 eV photon energy range. The photoelectron spectra were simulated starting from a first-principles band-structure calculation for the ground state, using the free-electron approximation for the final states, taking into account photohole lifetime effects and k(perpendicular to) broadening plus correlation effects, but ignoring transition matrix elements. The measured spin polarizations for the various k points investigated in the Gamma MLA plane of the Brillouin zone are found to be in fair enough agreement with the simulated ones, providing a strong support to the ground-state band-structure calculations. Possible origins for the departures between either simulations and experiments or previous and present experiments are discussed.

Published
2015

130. Polycrystalline Co2Mn-based Heusler thin films with high spin polarization and low magnetic damping.

Author

Guillemard, C., Petit-Watelot, S., Rojas-Sánchez, J.-C., Hohlfeld, J., Ghanbaja, J., Bataille, A., Le Fèvre, P., Bertran, F., and Andrieu, S.

Subjects
POLYCRYSTALLINE semiconductors, SPIN polarization, THIN films, FERROMAGNETIC materials, MAGNETIC materials, TRANSMISSION electron microscopy, FERROMAGNETIC resonance
Abstract

Spin-polarization and magnetic damping are measured for several polycrystalline films with each of them being made of a different single Co2Mn-based Heusler compound. As several epitaxial Co2Mn-based Heusler compounds are shown to be half-metal magnetic materials with full spin-polarization and ultralow magnetic damping, we explore here these properties but in polycrystalline films. Co2MnSi, Co2MnGe, and Co2MnGa thin films were grown on glass substrates and analyzed in situ by electron diffraction and spin-resolved photoemission and ex situ by transmission electron microscopy and ferromagnetic resonance. Despite the polycrystalline state of the films, they still exhibit high spin polarizations and very low magnetic damping coefficients. The latter are at least of the same order as the best epitaxial films using regular ferromagnetic materials. The key point to achieve such properties is to control the Heusler stoichiometry as best as possible. [ABSTRACT FROM AUTHOR]

Published
2019
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131. Orientational tuning of the Fermi sea of confined electrons at the SrTiO3 (110) and (111) surfaces

Author

Roedel T., C., Bareille, C., Fortuna, F., Bertran, F., Le Fevre, P., Gabay, M., Cubelos O., Hijano, Rozenberg M., J., Maroutian, T., Lecoeur, P., Santander-Syro A., F., Baumier, C., CSNSM PS1, Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), CSNSM INSTRU, Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut d'électronique fondamentale (IEF), and Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS]Physics [physics], OXIDE HETEROSTRUCTURES, QUANTUM-WELL STATES, Condensed Matter::Materials Science, Condensed Matter - Materials Science, GAS, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], LAALO3/SRTIO3 INTERFACE
Abstract

We report the existence of confined electronic states at the (110) and (111) surfaces of SrTiO3. Using angle-resolved photoemission spectroscopy, we find that the corresponding Fermi surfaces, subband masses, and orbital ordering are different from the ones at the (001) surface of SrTiO3. This occurs because the crystallographic symmetries of the surface and sub-surface planes, and the electron effective masses along the confinement direction, influence the symmetry of the electronic structure and the orbital ordering of the t2g manifold. Remarkably, our analysis of the data also reveals that the carrier concentration and thickness are similar for all three surface orientations, despite their different polarities. The orientational tuning of the microscopic properties of two-dimensional electron states at the surface of SrTiO3 echoes the tailoring of macroscopic (e.g. transport) properties reported recently in LaAlO3/SrTiO3 (110) and (111) interfaces, and is promising for searching new types of 2D electronic states in correlated-electron oxides., Accepted for publication as a Letter in Physical Review Applied

Published
2014

132. Spectroscopic and transport studies of Cox Fe1-x/MgO(001) -based magnetic tunnel junctions

Author

Andrieu, Stéphane, Calmels, Lionel, Hauet, Thomas, Bonell, Frédéric, Le Fèvre, P., Bertran, F., Institut Jean Lamour (IJL), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Matériaux et dispositifs pour l'Electronique et le Magnétisme (CEMES-MEM), Centre d'élaboration de matériaux et d'études structurales (CEMES), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), and Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS]Physics [physics], PACS number(s): 72.25.−b, 73.40.Gk, 81.15.Hi
Abstract

cited By 4; International audience; Fe1-xCox epitaxial layers were grown by molecular beam epitaxy and controlled using in situ characterization tools (electron diffraction, x-ray photoelectron, and Auger spectroscopies) in order to use these alloys in magnetic tunnel junctions. Thick films are shown to be BCC up to x=70%, whereas thin films grown on Fe(001) are BCC over the whole Co concentration range up to a critical thickness. Fe/Co intermixing is also examined in detail. The tunnel magnetoresistance and conductance of MgO-based magnetic tunnel junctions built with BCC Fe1-xCox electrodes show peculiar voltage dependencies. Their interpretation relies on spin- and symmetry-resolved photoemission measurements and ab initio calculations. The bulk and interfacial occupied states detected by photoemission are compared to the calculated ones. Experimental results and ab initio calculations are in good agreement. Finally, the experimental conductance curves are compared to the autoconvolution of the Δ1 density of states in which both bulk and interface states are taken into account.

Published
2014

133. Fe t_{2g} band dispersion and spin polarization in thin films of Fe_{3}O_{4}(0 0 1)/MgO(0 0 1): Half-metallicity of magnetite revisited

Author

Wang, Weimin, Mariot, J., Richter, Maria Christine, Heckmann, Olivier, Ndiaye, Waly, De Padova, P., Taleb-Ibrahimi, A., Le Fèvre, P., Bertran, F., Laboratoire de Physique des Matériaux et des Surfaces (LPMS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-CY Cergy Paris Université (CY)

Subjects
[PHYS]Physics [physics]
Published
2013

135. Entanglement and manipulation of the magnetic and spin–orbit order in multiferroic Rashba semiconductors

Author

Krempaský, J., primary, Muff, S., additional, Bisti, F., additional, Fanciulli, M., additional, Volfová, H., additional, Weber, A. P., additional, Pilet, N., additional, Warnicke, P., additional, Ebert, H., additional, Braun, J., additional, Bertran, F., additional, Volobuev, V. V., additional, Minár, J., additional, Springholz, G., additional, Dil, J. H., additional, and Strocov, V. N., additional

Published
2016
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136. Simple and advanced ferromagnet/molecule spinterfaces

Author

Gruber, M., additional, Ibrahim, F., additional, Djedhloul, F., additional, Barraud, C., additional, Garreau, G., additional, Boukari, S., additional, Isshiki, H., additional, Joly, L., additional, Urbain, E., additional, Peter, M., additional, Studniarek, M., additional, Da Costa, V., additional, Jabbar, H., additional, Bulou, H., additional, Davesne, V., additional, Halisdemir, U., additional, Chen, J., additional, Xenioti, D., additional, Arabski, J., additional, Bouzehouane, K., additional, Deranlot, C., additional, Fusil, S., additional, Otero, E., additional, Choueikani, F., additional, Chen, K., additional, Ohresser, P., additional, Bertran, F., additional, Le Fèvre, P., additional, Taleb-Ibrahimi, A., additional, Wulfhekel, W., additional, Hajjar-Garreau, S., additional, Wetzel, P., additional, Seneor, P., additional, Mattana, R., additional, Petroff, F., additional, Scheurer, F., additional, Weber, W., additional, Alouani, M., additional, Beaurepaire, E., additional, and Bowen, M., additional

Published
2016
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137. Spin to Charge Conversion at Room Temperature by Spin Pumping into a New Type of Topological Insulator:α-Sn Films

Author

Rojas-Sánchez, J.-C., primary, Oyarzún, S., additional, Fu, Y., additional, Marty, A., additional, Vergnaud, C., additional, Gambarelli, S., additional, Vila, L., additional, Jamet, M., additional, Ohtsubo, Y., additional, Taleb-Ibrahimi, A., additional, Le Fèvre, P., additional, Bertran, F., additional, Reyren, N., additional, George, J.-M., additional, and Fert, A., additional

Published
2016
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138. Enhanced magnetization at the Cr/MgO(001) interface

Author

Leroy, M.-A., primary, Bataille, A. M., additional, Wang, Q., additional, Fitzsimmons, M. R., additional, Bertran, F., additional, Le Fèvre, P., additional, Taleb-Ibrahimi, A., additional, Vlad, A., additional, Coati, A., additional, Garreau, Y., additional, Hauet, T., additional, Gatel, C., additional, Ott, F., additional, and Andrieu, S., additional

Published
2015
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140. Two-dimensional électron gas with hexagonal electronic structure at the surface of KTaO3(111)

Author

Bareille, C., Fortuna, F., Rödel, T., Gabay, M., Bertran, F., Taleb-Ibrahimi, A., Le Fèvre, P., Bibes, M., Barthélémy, Alain, Lecoeur, P., Guevara, J., J. Rozenberg, M., Santander-Syro, A.F., CSNSM PS2, Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Laboratoire de Physique des Solides (LPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), Hadrossek, Christine, Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), and Centre National de la Recherche Scientifique (CNRS)-THALES

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci]
Published
2013

141. The 2 root 3 x 2 root 3R30 surface reconstruction of alkali/Si(111):B semiconducting surfaces

Author

Tournier-Colletta, Cédric, Chaput, Laurent, Tejeda, Antonio, Cardenas, Luis A., Kierren, Bertrand, Malterre, Daniel, Fagot-Révurat, Yannick, Le Fèvre, P., Bertran, F., Taleb-Ibrahimi, A., Institut Jean Lamour (IJL), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), and Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
LEED, root 3-reconstructed semiconducting surfaces, XPS, STM, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], LAPW-DFT calculations, Alkalioverlayers
Abstract

Équipe 102 : Surfaces et Spectroscopies; International audience; The surface structure of alkali doped Si(111): B ultra-thin films has been studied by low-energy electron diffraction (LEED), X-ray photoemission spectroscopy (XPS) and scanning tunneling microscopy (STM). A comparative study of K/Si(111)-3 x 1 and K/Si(111):B-2 root 3 x 2 root 3R30 interfaces allowed us to determine the saturation coverage to be 0.5 monolayer in the later case. The 2 root 3-surface reconstruction is shown to be a common property of pure K, Rb, Cs materials and K0.4Rb0.6 alloys but progressively disappears if Rb is replaced by Ca. Taking into account the existence of two distinct boron sites in the ratio 1/3 as seen from B-1s core levels spectra, LAPW-DFT calculations have been carried out in order to optimize the atomic structure. As a result, alkali adatoms are shown to form trimers leading to a large modulation of the Si B bonds accompanied by an inhomogeneous doping of the dangling bonds in agreement with voltage dependent STM images

Published
2013

142. Novel two-dimensional electron gases at the surface of transition-metal oxides

Author

Santander-Syro, A.F., Bareille, C., Fortuna, F., Rödel, T., Gabay, M., Bertran, F., Taleb-Ibrahimi, A., Le Fèvre, P., Bibes, M., Barthélémy, Alain, Lecoeur, P., Guevara, J., J. Rozenberg, M., CSNSM PS2, Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Laboratoire de Physique des Solides (LPS), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Hadrossek, Christine, Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), and THALES-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci]
Published
2013

143. Novel two-dimensional electron gases at the surface of transition-metal oxides. 42nd

Author

Santander-Syro, A.F., Bareille, C., Fortuna, F., Rödel, T., Gabay, M., Bertran, F., Taleb-Ibrahimi, A., Le Fèvre, P., Bibes, M., Barthélémy, Alain, Lecoeur, P., Guevara, J., J. Rozenberg, M., Hadrossek, Christine, CSNSM PS2, Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Laboratoire de Physique des Solides (LPS), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), and THALES-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci]
Published
2013

144. Electronic structure and two-dimensional electron gas at the surface of SrTiO3

Author

Santander-Syro, A. F., Copie, O., Kondo, T., Fortuna, F., Stéphane Pailhès, Weht, R., Qiu, X. G., Bertran, F., Nicolaou, A., Taleb-Ibrahimi, A., Le Fèvre, P., Herranz, G., Bibes, M., Reyren, N., Apertet, Y., Lecoeur, P., Alain Barthélémy, Rozenberg, M. J., CSNSM PS2, Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Institut de Ciencia de materials de barcelone, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Institut d'électronique fondamentale (IEF), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Solides (LPS), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Hadrossek, Christine, Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and THALES [France]-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci]
Published
2012

145. Spin-Polarized Electron Tunneling in bcc FeCo/MgO/FeCo(001) Magnetic Tunnel Junctions

Author

Bonell, F, Hauet, Thomas, ANDRIEU, S, BERTRAN, F, Le Fèvre, P, Calmels, Lionel, Tejeda, A, Montaigne, F, Warot-Fonrose, Bénédicte, Belhadji, B, Nicolaou, A, Taleb-Ibrahimi, A, Institut Jean Lamour (IJL), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Centre d'élaboration de matériaux et d'études structurales (CEMES), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES [France]-Centre National de la Recherche Scientifique (CNRS), Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), Centre National de la Recherche Scientifique (CNRS)-THALES, and THALES-Centre National de la Recherche Scientifique (CNRS)

Subjects
molecular beam epitaxy, synchrotron, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], magnetoresistance, spin-resolved photoemission, spintronic, magnetic tunnel junction, material science
Abstract

International audience; In combining spin-and symmetry-resolved photoemission, magnetotransport measurements and ab initio calculations we detangled the electronic states involved in the electronic transport in Fe 1Àx Co x ð001Þ=MgO=Fe 1Àx Co x ð001Þ magnetic tunnel junctions. Contrary to previous theoretical predictions , we observe a large reduction in TMR (from 530 to 200% at 20 K) for Co content above 25 atomic % as well as anomalies in the conductance curves. We demonstrate that these unexpected behaviors originate from a minority spin state with Á 1 symmetry that exists below the Fermi level for high Co concentration. Using angle-resolved photoemission, this state is shown to be a two-dimensional state that occurs at both Fe 1Àx Co x ð001Þ free surface, and more importantly at the interface with MgO. The combination of this interface state with the peculiar density of empty states due to chemical disorder allows us to describe in details the complex conduction behavior in this system. Since the discovery of giant magnetoresistance (GMR) in spin valves in 1988 [1], a new branch of physics referred to as spintronics has considerably developed. The discovery of the large tunnel magnetoresistance (TMR) in 1995 [2], the prediction of the spin-transfer mechanism in 1996 [3,4], and the demonstration of spin-dependent coherent tunnel-ing in MgO-based epitaxial MTJs in 2001-2004 [5–10], have largely contributed to developments in this field. Currently, a number of new areas are being explored, such as rf oscillators, devices and memories based on the spin-transfer-torque effect, electric field assisted switching , magnonics, or spincaloritronics [11]. In addition, industrial-scale devices such as magnetic recording heads already use the exceptional electrical properties of GMR and TMR. The technology transfer from research to industry continues today, with MRAM demonstrators based on MgO-based MTJs [12] and rf oscillators using spintronics devices. While commercialization as well as broad utilization into various areas of research has been rapid for spin-tronic devices, in many cases a full understanding of the underlying physics is lacking. MgO-based MTJs with FeCo or FeCoB electrodes are a striking example of this situation. FeCoðBÞ=MgO=FeCoðBÞð001Þ multilayers, fabricated by molecular beam epitaxy (MBE) or sputtering deposition are widely utilized for their high spin current injection efficiency and exceptional electrical sensitivity to any change in the magnetic configuration of the electrodes. Because of the huge TMR predicted by ab initio calculation for the equimolar and B2 ordered Fe 0:5 Co 0:5 alloy and for pure bcc Co (1000%–6000% at 0 K [13]), bcc FeCo(001) electrodes are now extensively used in MTJ fabrication. However, the situation is not so clear regarding the reported results. First, large TMR were actually obtained on MBE grown Fe=bcc Co=MgO=Co=Feð001Þ [14]. However, a heating of the whole stacking up to 250 C during 30 minutes suggest a possible alloying between Fe and Co. On the other hand, contrary to expectations, epitaxial Fe 0:5 Co 0:5 =MgO=Feð001Þ and Fe=MgO=Feð001Þ MTJs exhibit the same TMR [15]. It should be noted that the B2 order assumed in Ref. [13] is not observed. Finally, reported TMR of sputtered FeCo=MgO=FeCoð001Þ MTJs present a nonmonotonic dependence as a function of the Co concentration with a maximum around 25% of Co [16]. The detailed effect of Co alloying into Fe on the spin-dependent tunneling remains therefore obscure. In this Letter, we explain quantitatively the unexpected transport properties observed in FeCo=MgO=FeCoð001Þ MTJs. We demonstrate that transport measurements alone are not sufficient to complete the current understanding of this system, and that spin-, symmetry-, and angle-resolved photoemission, together with DFT calculations taking into account the chemical disorder, offer a unique path to probing directly the tunneling electrons. We use a specific photoemission experiment to untangle the different Bloch waves responsible for the conduction along (001) as a function of their symmetry (Á 1 or Á 5) and spin state (majority " or minority #), in contrast to standard transport measurements where all these contributions are mixed. bcc MgO-based MTJs with Fe 1Àx Co x ð001Þ electrodes were grown by coevaporation using MBE. The epitaxial relationship, growth mode, and surface flatness were controlled using reflection high energy electron diffraction (RHEED). In addition, the evaporation rates of the Co and Fe sources, and consequently the alloys stoichiometry, were accurately controlled by recording the intensity

Published
2012

146. Novel two-dimensional electron gases at the surface of transition-metal oxides: from orbital ordering to orbital symmetry reconstruction

Author

Santander-Syro, A. F., Bareille, C., Fortuna, F., Copie, O., Gabay, M., Bertran, F., Taleb-Ibrahimi, A., Le Fèvre, P., Herranz, G., Reyren, N., Bibes, M., Barthéléemy, A., Lecoeur, P., Guevara, J., J. Rozenberg, M., CSNSM PS2, Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Laboratoire de Physique des Solides (LPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Institut de Ciencia de materials de barcelone, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), Institut d'électronique fondamentale (IEF), Hadrossek, Christine, Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), and Centre National de la Recherche Scientifique (CNRS)-THALES

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci]
Published
2012

148. Unveiling a two-dimensional electron gas with universal subbands at the surface of SrTiO3

Author

F. Santander-Syro, A. F., Copie, O., Kondo, T., Fortuna, F., Pailhès, S., Weht, R., G. Qiu, X., Bertran, F., Nicolaou, A., Taleb-Ibrahimi, A., Le Fèvre, P., Herranz, G., Bibes, M., Reyren, N., Apertet, Y., Lecoeur, P., Barthélémy, Alain, J. Rozenberg, M., CSNSM PS2, Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Institut de Ciencia de materials de barcelone, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Institut d'électronique fondamentale (IEF), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), THALES [France]-Centre National de la Recherche Scientifique (CNRS), Hadrossek, Christine, and Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci]
Published
2011

149. A novel two-dimensional electron gas with universal subbands at the surface of SrTiO3

Author

Santander-Syro, A. F., Copie, O., Kondo, T., Fortuna, F., Pailhès, S., Weht, R., G. Qiu, X., Bertran, F., Nicolaou, A., Taleb-Ibrahimi, A., Le Fèvre, P., Herranz, G., Bibes, M., Reyren, N., Apertet, Y., Lecoeur, P., Barthélémy, Alain, J. Rozenberg, M., Hadrossek, Christine, CSNSM PS2, Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Institut de Ciencia de materials de barcelone, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES [France]-Centre National de la Recherche Scientifique (CNRS), Institut d'électronique fondamentale (IEF), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Solides (LPS), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, Centre National de la Recherche Scientifique (CNRS)-THALES, and Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci]
Published
2011

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