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1. Volatiles and Refractories in Surface-Bounded Exospheres in the Inner Solar System

Author

Alexey A. Berezhnoy, Rosemary M. Killen, Jasper Halekas, B. D. Teolis, Cesare Grava, Masaki N. Nishino, Jim M. Raines, Mehdi Benna, Christina Plainaki, Audrey Vorburger, François Leblanc, Ronald J. Vervack, Menelaos Sarantos, Orenthal J. Tucker, Southwest Research Institute [San Antonio] (SwRI), NASA Goddard Space Flight Center (GSFC), University of Maryland [Baltimore], Sternberg Astronomical Institute [Moscow], Lomonosov Moscow State University (MSU), Institute of Physics [Kazan] (IoP), Kazan Federal University (KFU), Department of Physics and Astronomy [Iowa City], University of Iowa [Iowa City], HELIOS - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency [Sagamihara] (JAXA), Italian Space Agency, Department of Climate and Space Sciences and Engineering (CLaSP), University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Physikalisches Institut [Bern], Universität Bern [Bern], and Open Access funding provided by Universität Bern. Grava was supported by LRO, funded by NASA through contract NNG05EC87C. Berezhnoy was supported by RFBR grant No. 18-03-00726. Halekas was supported by SSERVI and NASA grant 80NSSC20K0311. Raines was supported by the NASA Discovery Data Analysis Program, grants NNX15AL01G and 80NSSC19K0204. Vervack was supported by NASA grant 80NSSC18K0857 (subcontract to JH-APL).

Subjects
Volatiles, Solar System, Materials science, 010504 meteorology & atmospheric sciences, Solar wind, chemistry.chemical_element, 01 natural sciences, Article, Astrobiology, Physics::Geophysics, Neon, Neutrals, 0103 physical sciences, Physics::Atomic and Molecular Clusters, Moon, 010303 astronomy & astrophysics, Helium, 0105 earth and related environmental sciences, Ions, Argon, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Refractories, Noble gas, Astronomy and Astrophysics, Mercury, Planetary science, chemistry, 13. Climate action, Space and Planetary Science, Magnetosphere, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, Exosphere
Abstract

Volatiles and refractories represent the two end-members in the volatility range of species in any surface-bounded exosphere. Volatiles include elements that do not interact strongly with the surface, such as neon (detected on the Moon) and helium (detected both on the Moon and at Mercury), but also argon, a noble gas (detected on the Moon) that surprisingly adsorbs at the cold lunar nighttime surface. Refractories include species such as calcium, magnesium, iron, and aluminum, all of which have very strong bonds with the lunar surface and thus need energetic processes to be ejected into the exosphere. Here we focus on the properties of species that have been detected in the exospheres of inner Solar System bodies, specifically the Moon and Mercury, and how they provide important information to understand source and loss processes of these exospheres, as well as their dependence on variations in external drivers.

Published
2021
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2. Anisotropic cosmological models in Horndeski gravity

Author

Sergey V. Sushkov, Alexei A. Starobinsky, Ruslan K. Muharlyamov, Rafkat Galeev, Mikhail S. Volkov, Institute of Physics [Kazan] (IoP), Kazan Federal University (KFU), L.D. Landau Institute for Theoretical Physics of RAS, Russian Academy of Sciences [Moscow] (RAS), Institut Denis Poisson (IDP), Centre National de la Recherche Scientifique (CNRS)-Université de Tours (UT)-Université d'Orléans (UO), and Centre National de la Recherche Scientifique (CNRS)-Université de Tours-Université d'Orléans (UO)

Subjects
High Energy Physics - Theory, velocity, cosmological model, coupling: nonminimal, gravitation: model, perturbation, General relativity, Initial singularity, alternative theories of gravity, FOS: Physical sciences, Context (language use), General Relativity and Quantum Cosmology (gr-qc), 01 natural sciences, General Relativity and Quantum Cosmology, space-time: Bianchi: Type I, Cosmology, photon: velocity, Gravitation, Theoretical physics, Singularity, 0103 physical sciences, inflation, initial state, 010306 general physics, Physics, Inflation (cosmology), space-time: anisotropy, [PHYS.HTHE]Physics [physics]/High Energy Physics - Theory [hep-th], 010308 nuclear & particles physics, gravitational radiation: primordial, gravitational radiation, stability, singularity, field theory: scalar, High Energy Physics - Theory (hep-th), gravitation, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], k-essence, Scalar field
Abstract

It was found recently that the anisotropies in the homogeneous Bianchi I cosmology considered within the context of a specific Horndeski theory are damped near the initial singularity instead of being amplified. In this work we extend the analysis of this phenomenon to cover the whole of the Horndeski family. We find that the phenomenon is absent in the K-essence and/or Kinetic Gravity Braiding theories, where the anisotropies grow as one approaches the singularity. The anisotropies are damped at early times only in more general Horndeski models whose Lagrangian includes terms quadratic and cubic in second derivatives of the scalar field. Such theories are often considered as being inconsistent with the observations because they predict a non-constant speed of gravitational waves. However, the predicted value of the speed at present can be close to the speed of light with any required precision, hence the theories actually agree with the present time observations. We consider two different examples of such theories, both characterized by a late self-acceleration and an early inflation driven by the non-minimal coupling. Their anisotropies show a maximum at intermediate times and approach zero at early and late times. The early inflationary stage exhibits an instability with respect to inhomogeneous perturbations, suggesting that the initial state of the universe should be inhomogeneous. However, more general Horndeski models may probably be stable., Comment: 21 pages, several figures

Published
2021
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3. Signal feedback applications in low-field NMR and MRI

Author

Pierre-Jean Nacher, V. V. Kuzmin, Laboratoire Kastler Brossel (LKB (Lhomond)), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institute of Physics [Kazan] (IoP), Kazan Federal University (KFU), Supported in part by the FPGG (P.-G. de Gennes) foundation, and ANR-12-IS04-0006,IMAGINE,Etudes RMN d'effets non-linéaires induits par l'aimantation(2012)

Subjects
Nuclear and High Energy Physics, Preamplifier, Capacitive sensing, Acoustics, Biophysics, quality factor, Low frequency, 010402 general chemistry, 01 natural sciences, Biochemistry, 030218 nuclear medicine & medical imaging, 03 medical and health sciences, 0302 clinical medicine, signal feedback, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Physics, [PHYS.PHYS.PHYS-ATOM-PH]Physics [physics]/Physics [physics]/Atomic Physics [physics.atom-ph], Bandwidth (signal processing), Q-factor, low-field MRI, Condensed Matter Physics, Inductive coupling, 0104 chemical sciences, Radiation damping, Electromagnetic coil, Q factor, [PHYS.PHYS.PHYS-MED-PH]Physics [physics]/Physics [physics]/Medical Physics [physics.med-ph], radiation damping, Low-field NMR
Abstract

International audience; Tuned pick-up coils with high quality factors $Q$ are used in NMR and MRI for high-sensitivity and low-noise detection. However, large $Q$-factors introduce bandwidth issues at low frequency and the associated enhanced currents may cause significant radiation damping effects, especially with hyperpolarised samples. Signal feedback can be used to actively control these currents and adjust the detection bandwidth without resistive losses. Capacitive and inductive coupling methods are compared using detailed models and the operating conditions for efficient feedback with negligible noise penalty are discussed. Several high-impedance commercial preamplifiers have been found to affect the resonance characteristics of tuned coils in a gain-dependent way, or could not be used in low-frequency NMR because of oscillations at large positive gain. This is attributed to an undocumented internal feedback, and could be neutralised using external feedback. The implementation of an inductive coupling scheme to feed a suitably amplified phase-adjusted signal back into the PU coils of low-field NMR systems is described, and three experimental applications are reported. One system is used for NMR studies of distant dipolar field effects in highly polarized liquid $^3$He without or with radiation damping. The moderate intrinsic $Q$-factor ($\approx$7) could be reduced (down to 1) or increased (up to 100) to control transient maser oscillations. Another system was used for MRI of water samples around 2~mT with $Q\approx$190 Litz-wire detection coils. The detection bandwidth was increased by actively reducing the $Q$-factor to obtain uniform sensitivities in images and avoid artifacts introduced by intensity corrections. Finally, parallel acquisition in MRI was performed using two separately tuned detection coils placed above and below the sample. They were actively decoupled using two feedback systems. For an imaging field of view smaller than the sample, artifact-free unfolded images demonstrate the efficiency of this active coil decoupling scheme.

Published
2019
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4. Coherent long-range transfer of angular momentum between magnon Kittel modes by phonons

Author

G. de Loubens, Nicolas Vukadinovic, Gerrit E. W. Bauer, A. A. Fuad, V. V. Naletov, Herve Hurdequint, A. N. Litvinenko, Andrei Slavin, Kyongmo An, Laurent Vila, V. S. Tiberkevich, Nathan Beaulieu, Ryuhei Kohno, Olivier Klein, Ursula Ebels, J. Ben Youssef, SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institute of Physics [Kazan] (IoP), Kazan Federal University (KFU), Laboratoire Nano-Magnétisme et Oxydes (LNO), Service de physique de l'état condensé (SPEC - UMR3680), 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)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Laboratoire de Physique des Solides (LPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de magnétisme de Bretagne (LMB), Université de Brest (UBO)-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Dassault Aviation, WPI Advanced Institute for Materials Research (WPI-AIMR), Tohoku University [Sendai], and Oakland University

Subjects
Angular momentum, Materials science, Phonon, Yttrium iron garnet, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, chemistry.chemical_compound, Condensed Matter::Materials Science, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, Spin (physics), Magnetization dynamics, Condensed Matter - Materials Science, Condensed matter physics, Condensed Matter - Mesoscale and Nanoscale Physics, Magnon, Materials Science (cond-mat.mtrl-sci), Gadolinium gallium garnet, 021001 nanoscience & nanotechnology, Ferromagnetic resonance, chemistry, Condensed Matter::Strongly Correlated Electrons, 0210 nano-technology
Abstract

We report a ferromagnetic resonance study of an electrically insulating magnetic bi-layer consisting of two yttrium iron garnet (YIG) films epitaxially grown on both sides of a non-magnetic gadolinium gallium garnet (GGG) slab. We show that standing transverse sound waves couple the coherent magnetization dynamics of the two YIG films half millimeter apart through the magnetoelastic interaction, periodically modulating the microwave absorption as a function of frequency. Constructive and destructive interferences between the dynamics of the two YIG layers is observed. This long range coherent coupling by phononic angular momentum currents through non-magnetic dielectric waveguide brings new functionalities to insulator hybrid spin circuits and devices.

Published
2019
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5. Direct observation of dynamic modes excited in a magnetic insulator by pure spin current

Author

M. Evelt, Vincent Cros, J. Ben Youssef, V. V. Naletov, Vladimir O. Bessonov, Martin Collet, Paolo Bortolotti, G. de Loubens, Olivier Klein, José L. Prieto, Manuel Muñoz, Sergej O. Demokritov, Vladislav E. Demidov, Abdelmadjid Anane, Institute for Applied Physics and Center for Nanotechnology, University of Münster, M.N. Mikheev Institute of Metal Physics (IMP), Ural Branch of Russian Academy of Sciences (UB RAS), Instituto de Sistemas Optoelectrónicos y Microtecnología, Universidad Politécnica de Madrid (UPM), Instituto de Microelectronica de Madrid (IMM), Centro Nacional de Microelectronica [Spain] (CNM)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Laboratoire de magnétisme de Bretagne (LMB), Université de Brest (UBO)-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Nano-Magnétisme et Oxydes (LNO), Service de physique de l'état condensé (SPEC - UMR3680), 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)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institute of Physics [Kazan] (IoP), Kazan Federal University (KFU), SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, German Research Foundation, Agence Nationale de la Recherche (France), Ministry of Education and Science of the Russian Federation, Kazan Federal University, Westfälische Wilhelms-Universität Münster (WWU), Instituto Carlos I de Fisica Teorica y Computacional, Universidad de Granada (UGR), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Théorique de la Matière Condensée (LPTMC), Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Recherche translationelle relations hôte-pathogènes, Université de Lille-Centre Hospitalier Régional Universitaire [Lille] (CHRU Lille), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Centro Nacional de Microelectronica [Spain] (CNM), Westfälische Wilhelms-Universität Münster = University of Münster (WWU), and THALES [France]-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Yttrium iron garnet, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Article, Magnetization, chemistry.chemical_compound, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, 010306 general physics, Magnonics, [PHYS]Physics [physics], Magnetization dynamics, Multidisciplinary, Condensed matter physics, Spin polarization, Spintronics, Condensed Matter - Mesoscale and Nanoscale Physics, 021001 nanoscience & nanotechnology, chemistry, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], Mode coupling, Condensed Matter::Strongly Correlated Electrons, 0210 nano-technology, Excitation
Abstract

Excitation of magnetization dynamics by pure spin currents has been recently recognized as an enabling mechanism for spintronics and magnonics, which allows implementation of spin-torque devices based on low-damping insulating magnetic materials. Here we report the first spatially-resolved study of the dynamic modes excited by pure spin current in nanometer-thick microscopic insulating Yttrium Iron Garnet disks. We show that these modes exhibit nonlinear self-broadening preventing the formation of the self-localized magnetic bullet, which plays a crucial role in the stabilization of the single-mode magnetization oscillations in all-metallic systems. This peculiarity associated with the efficient nonlinear mode coupling in low-damping materials can be among the main factors governing the interaction of pure spin currents with the dynamic magnetization in high-quality magnetic insulators., This research was partially supported by the Deutsche Forschungsgemeinschaft, the ANR Grant Trinidad (ASTRID 2012 program), and the program Megagrant No. 14.Z50.31.0025 of the Russian Ministry of Education and Science. M. C. acknowledges DGA for financial support. V. V. N. acknowledges support from the Competitive Growth of KFU.

Published
2016
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6. Ultra-fast perpendicular Spin Orbit Torque MRAM

Author

Gilles Gaudin, Claire Hamelin, Nathalie Lamard, Kevin Garello, V. V. Naletov, Ioan Mihai Miron, Juergen Langer, M. Cubukcu, Liliana D. Buda-Prejbeanu, Thomas Brächer, Olivier Klein, Berthold Ocker, Olivier Boulle, G. de Loubens, N. Mikuszeit, Pietro Gambardella, Marie-Claire Cyrille, SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Department of Materials [ETH Zürich] (D-MATL), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Laboratoire Nano-Magnétisme et Oxydes (LNO), Service de physique de l'état condensé (SPEC - UMR3680), 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)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institute of Physics [Kazan] (IoP), Kazan Federal University (KFU), and Singulus technology AG

Subjects
010302 applied physics, Magnetoresistive random-access memory, Range (particle radiation), Condensed Matter - Materials Science, Materials science, Spintronics, business.industry, Cache memory, MRAM, spin-orbit torque-MRAM (SOT-MRAM), spin transfer, spin-orbit torque, spintronics, spin transfer torque-magnetic random access memory (STT-MRAM), Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, 02 engineering and technology, Nanosecond, 021001 nanoscience & nanotechnology, 01 natural sciences, Electronic, Optical and Magnetic Materials, Tunnel magnetoresistance, Magnetization, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], 0103 physical sciences, Perpendicular, Torque, Optoelectronics, Electrical and Electronic Engineering, 0210 nano-technology, business
Abstract

We demonstrate ultra-fast (down to 400 ps) bipolar magnetization switching of a three-terminal perpendicular Ta/FeCoB/MgO/FeCoB magnetic tunnel junction. The critical current density rises significantly as the current pulse shortens below 10 ns, which translates into a minimum in the write energy in the ns range. Our results show that SOT-MRAM allows fast and low power write operations, which renders it promising for non-volatile cache memory applications., 15 pages, 3 figures

Published
2015
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7. Conduction of spin currents through insulating antiferromagnetic oxides

Author

Hahn, Christian, de Loubens, Grégoire, Naletov, Vladimir, Ben Youssef, Jamal, Klein, Olivier, Viret, Michel, Laboratoire Nano-Magnétisme et Oxydes (LNO), Service de physique de l'état condensé (SPEC - UMR3680), 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)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institute of Physics [Kazan] (IoP), Kazan Federal University (KFU), Laboratoire de magnétisme de Bretagne (LMB), Université de Brest (UBO)-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), and Ben Youssef, Jamal

Subjects
[PHYS]Physics [physics], [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], [PHYS.COND] Physics [physics]/Condensed Matter [cond-mat], ComputingMilieux_MISCELLANEOUS, [PHYS] Physics [physics]
Abstract

International audience

Published
2014

8. Electron spin resonance and exchange paths in the orthorhombic dimer system Sr2VO4

Author

Deisenhofer, Joachim, Schaile, S., Teyssier, Jeremie, Wang, Zhe, Hemmida, M., Krug Von Nidda, H.-A., Eremina, R. M., Eremin, M. V., Viennois, Romain, Giannini, E., Loidl, A., Van Der Marel, Dirk, Experimentalphysik V, Center for Electronic Correlations and Magnetism, Institute for Physics, Universität Augsburg [Augsburg], DPMC, Université de Genève, Université de Genève (UNIGE), E. K. Zavoisky Physical Technical Institute, Institute of Physics [Kazan] (IoP), Kazan Federal University (KFU), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), and Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC)

Subjects
Condensed Matter - Strongly Correlated Electrons, 76.30.-v, Strongly Correlated Electrons (cond-mat.str-el), FOS: Physical sciences, Condensed Matter::Strongly Correlated Electrons, ddc:500.2, [PHYS.COND.CM-SCE]Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el]
Abstract

We report on magnetization and electron spin resonance (ESR) measurements of Sr$_{2}$VO$_4$ with orthorhombic symmetry. In this dimer system the $V^{4+}$ ions are in tetrahedral environment and are coupled by an antiferromagnetic intra-dimer exchange constant $J/k_B \approx$ 100 K to form a singlet ground state without any phase transitions between room temperature and 2 K. Based on an extended-H\"{u}ckel-Tight-Binding analysis we identify the strongest exchange interaction to occur between two inequivalent vanadium sites via two intermediate oxygen ions. The ESR absorption spectra can be well described by a single Lorentzian line with an effective g-factor $g$ = 1.89. The temperature dependence of the ESR intensity is well described by a dimer model in agreement with the magnetization data. The temperature dependence of the ESR linewidth can be modeled by a superposition of a linear increase with temperature with a slope $\alpha$ = 1.35 Oe/K and a thermally activated behavior with an activation energy $\Delta/k_B$ = 1418 K, both of which point to spin-phonon coupling as the dominant relaxation mechanism in this compound., Comment: 5 pages, 4 figures

Published
2012
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