32 results on '"Frédéric Petroff"'
Search Results
2. Recovering ferromagnetic metal surfaces to fully exploit chemistry in molecular spintronics
- Author
-
Marta Galbiati, Sophie Delprat, Michele Mattera, Samuel Mañas-Valero, Alicia Forment-Aliaga, Sergio Tatay, Cyrile Deranlot, Pierre Seneor, Richard Mattana, and Frédéric Petroff
- Subjects
Physics ,QC1-999 - Abstract
Organic spintronics is a new emerging field that promises to offer the full potential of chemistry to spintronics, as for example high versatility through chemical engineering and simple low cost processing. However, one key challenge that remains to be unlocked for further applications is the high incompatibility between spintronics key materials such as high Curie temperature Co, Ni, Fe (and their alloys) and wet chemistry. Indeed, the transition metal proneness to oxidation has so far hampered the integration of wet chemistry processes into the development of room temperature organic spintronics devices. As a result, they had mainly to rely on high vacuum physical processes, restraining the choice of available organic materials to a small set of sublimable molecules. In this letter, focusing on cobalt as an example, we show a wet chemistry method to easily and selectively recover a metallic surface from an air exposed oxidized surface for further integration into spintronics devices. The oxide etching process, using a glycolic acid based solution, proceeds without increasing the surface roughness and allows the retrieval of an oxygen-free chemically active cobalt layer. This unlocks the full potential of wet chemistry processes towards room temperature molecular spintronics with transition metals electrodes. We demonstrate this by the grafting of alkylthiols self-assembled monolayers on recovered oxidized cobalt surfaces.
- Published
- 2015
- Full Text
- View/download PDF
3. Very Long Term Stabilization of a 2D Magnet down to the Monolayer for Device Integration
- Author
-
Bernard Servet, Sophie Collin, Pierre Seneor, Aymeric Vecchiola, Marta Galbiati, Pomme Hirschauer, Bruno Dlubak, Frédéric Petroff, Florian Godel, Victor Zatko, Andrés Cantarero, Marie-Blandine Martin, Karim Bouzehouane, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Thales Research and Technology [Palaiseau], and THALES
- Subjects
010302 applied physics ,[PHYS]Physics [physics] ,Materials science ,Spintronics ,Nanotechnology ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Term (time) ,Fragility ,Ferromagnetism ,Magnet ,0103 physical sciences ,Monolayer ,Materials Chemistry ,Electrochemistry ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,0210 nano-technology ,ComputingMilieux_MISCELLANEOUS - Abstract
2D materials have recently demonstrated a strong potential for spintronic applications. This has been further reinforced by the discovery of ferromagnetic 2D layers. Nevertheless, the fragility of ...
- Published
- 2020
4. Band-structure spin-filtering in vertical spin valves based on chemical vapor deposited WS2
- Author
-
Sophie Collin, Jean-Christophe Charlier, Bernard Servet, Pierre Brus, Karim Bouzehouane, Pierre Seneor, Frédéric Petroff, Mauro Och, Marta Galbiati, Aymeric Vecchiola, Florian Godel, Marie-Blandine Martin, Pawel Palczynski, Odile Bezencenet, Simon M-M Dubois, Victor Zatko, Bruno Dlubak, Cecilia Mattevi, The Royal Society, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Institut de la matière condensée et des nanosciences / Institute of Condensed Matter and Nanosciences (IMCN), Université Catholique de Louvain = Catholic University of Louvain (UCL), Imperial College London, Thales Research and Technology [Palaiseau], and THALES
- Subjects
Materials science ,Tungsten disulfide ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,Condensed Matter::Materials Science ,Transition metal ,tungsten disulfide ,Condensed Matter::Superconductivity ,spin filtering ,General Materials Science ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,Nanoscience & Nanotechnology ,Electronic band structure ,2D ,Spin-½ ,[PHYS]Physics [physics] ,spintronics ,Spin filtering ,Condensed matter physics ,Spintronics ,business.industry ,General Engineering ,semiconductor ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,magnetic tunnel junction ,0104 chemical sciences ,Tunnel magnetoresistance ,Semiconductor ,chemistry ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology ,business - Abstract
International audience; We report on spin transport in WS2-based 2D-magnetic tunnel junctions (2D-MTJs), unveiling a band structure spin filtering effect specific to the transition metal dichalcogenides (TMDCs) family. WS2 mono-, bi-, and trilayers are derived by a chemical vapor deposition process and further characterized by Raman spectroscopy, atomic force microscopy (AFM), and photoluminescence spec-troscopy. The WS2 layers are then integrated in complete Co/Al2O3 /WS2/Co MTJ hybrid spin-valve structures. We make use of a tunnel Co/Al2O3 spin analyzer to probe the extracted spin-polarized current from the WS2/Co interface and its evolution as a function of WS2 layer thicknesses. For monolayer WS2, our technological approach enables the extraction of the largest spin signal reported for a TMDC-based spin valve, corresponding to a spin polarization of PCo/WS2 = 12%. Interestingly, for bi-and trilayer WS2, the spin signal is reversed, which indicates a switch in the mechanism of interfacial spin extraction. With the support of ab initio calculations, we propose a model to address the experimentally measured inversion of the spin polarization based on the change in the WS2 band structure while going from monolayer (direct bandgap) to bilayer (indirect bandgap). These experiments illustrate the rich potential of the families of semiconducting 2D materials for the control of spin currents in 2D-MTJs.
- Published
- 2019
5. Perpendicular magnetic anisotropy and intralayer interactions in a single layer of CoPt nanoparticles
- Author
-
Jolanta Stankiewicz, Fernando Bartolomé, L.M. García, Frédéric Petroff, Cyrile Deranlot, Adriana I. Figueroa, Julio C. Cezar, Javier Rubín, and Juan Bartolomé
- Subjects
Materials science ,Condensed matter physics ,Magnetometer ,Transition temperature ,Nanoparticle ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,law.invention ,SQUID ,Ferromagnetism ,law ,Phase (matter) ,Coupling (piping) ,General Materials Science ,Deposition (law) - Abstract
The multilayer films [Al2O3/tCo Co/tPt Pt]N, produced by sequential deposition of Co and Pt on alumina consist in layers of CoPt alloyed nanoparticles. They show perpendicular magnetic anisotropy (PMA) below a freezing temperature Tf, an asperomagnetic-like phase below that temperature, and hard ferromagnetic ordering below a transition temperature T1 < Tf. A single layer granular film (N = 1) with deposition thicknesses tCo=0.7 nm, tPt=1.5 nm and particle diameter of 3 nm is presently studied. SQUID magnetometry shows that a single layer presents the three phases as well. Para-, aspero-and ferromagnetic phases are observed upon lowering the temperature, with transition temperatures Tf ≈ 375 K and T1 ≈ 200 K, respectively. In addition, the PMA persists, proving that there is no interlayer coupling in the multilayer system. SQUID results also reveal a core-shell structure in the CoPt nanoparticles.
- Published
- 2019
6. Insulator-to-Metallic Spin-Filtering in 2D-Magnetic Tunnel Junctions Based on Hexagonal Boron Nitride
- Author
-
Robert S. Weatherup, Jean-Christophe Charlier, John Robertson, Stephan Hofmann, Pierre Seneor, Marie-Blandine Martin, Piran R. Kidambi, Maëlis Piquemal-Banci, Stéphane Xavier, Bruno Dlubak, Albert Fert, Abdelmadjid Anane, Sabina Caneva, Karim Bouzehouane, Regina Galceran, Florian Godel, Frédéric Petroff, Simon M-M Dubois, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Laboratory for Photovoltaics Luxembourg, University of Luxembourg [Luxembourg], University of Cambridge [UK] (CAM), Thales Research & Technology France, THALES, Unité de Physique-Chimie et physique des matériaux (LLN), and Université Catholique de Louvain = Catholic University of Louvain (UCL)
- Subjects
Materials science ,General Physics and Astronomy ,Hexagonal boron nitride ,Insulator (electricity) ,02 engineering and technology ,Chemical vapor deposition ,01 natural sciences ,chemical vapor deposition ,Metal ,Ab initio quantum chemistry methods ,0103 physical sciences ,General Materials Science ,hexagonal boron nitride ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,010306 general physics ,spintronics ,Spin filtering ,Spintronics ,Condensed matter physics ,General Engineering ,[CHIM.MATE]Chemical Sciences/Material chemistry ,021001 nanoscience & nanotechnology ,2D materials ,visual_art ,visual_art.visual_art_medium ,0210 nano-technology - Abstract
International audience; We report on the integration of atomically thin 2D insulating hexagonal boron nitride (h-BN) tunnel barriers into magnetic tunnel junctions (2D-MTJs) by fabricating two illustrative systems (Co/h-BN/Co and Co/h-BN/Fe) and by discussing h-BN potential for metallic spin filtering. The h-BN is directly grown by chemical vapor deposition on prepatterned Co and Fe stripes. Spin-transport measurements reveal tunnel magneto-resistances in these h-BN-based MTJs as high as 12% for Co/h-BN/h-BN/Co and 50% for Co/h-BN/Fe. We analyze the spin polarizations of h-BN/Co and h-BN/Fe interfaces extracted from experimental spin signals in light of spin filtering at hybrid chemisorbed/ physisorbed h-BN, with support of ab initio calculations. These experiments illustrate the strong potential of h-BN for MTJs and are expected to ignite further investigations of 2D materials for large signal spin devices.
- Published
- 2018
7. Investigating magnetic proximity effects at ferrite/Pt interfaces
- Author
-
Frédéric Petroff, Stéphane Collin, Jean-Baptiste Moussy, Andrei Rogalev, Vicent Cros, Richard Mattana, F. Wilhelm, Abdelmadjid Anane, Cyrile Deranlot, Manuel Collet, Katharina Ollefs, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES [France]-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, European Synchrotron Radiation Facility (ESRF), and Centre National de la Recherche Scientifique (CNRS)-THALES
- Subjects
[PHYS]Physics [physics] ,Materials science ,Physics and Astronomy (miscellaneous) ,Magnetic domain ,Spintronics ,Condensed matter physics ,Yttrium iron garnet ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Ferromagnetic resonance ,Magnetic susceptibility ,chemistry.chemical_compound ,Condensed Matter::Materials Science ,Nuclear magnetic resonance ,Ferromagnetism ,Magnetic shape-memory alloy ,chemistry ,Magnet ,0103 physical sciences ,Condensed Matter::Strongly Correlated Electrons ,010306 general physics ,0210 nano-technology - Abstract
International audience; Spintronic devices based on pure spin currents have drawn a lot of attention during the last few years for low energy device design. One approach to generate pure spin currents is to combine a metallic or insulating ferromagnetic layer with a non-magnetic metallic layer with a large spin-orbit coupling. A recent controversy has arisen in the possible role of magnetic proximity effects at ferromagnetic/ non-magnetic interfaces, which can hamper the understanding of pure spin current generation mechanisms. While magnetic proximity effects have been frequently observed at ferromagnetic metal/non-magnetic interfaces, there are only a few studies on ferromagnetic insulator/non-magnetic interfaces. Regarding the use of ferromagnetic insulators, the focus has been mainly on yttrium iron garnet (YIG). However, investigation of induced magnetic moments at YIG/Pt interfaces has engendered contradictory results. Here, we propose to study insulating ferrites for which electronic and magnetic properties can be modulated. Magnetic proximity effects have been investigated at MnFe 2 O 4 /Pt, CoFe 2 O 4 /Pt, and NiFe 2 O 4 /Pt interfaces by X-ray circular magnetic dichroism (XMCD) measurements at the Pt L 3 edge. Although hybridization with Pt seems to be different among the ferrites, we do not detect any XMCD signal as the signature of an induced magnetism in Pt. We have then studied the Fe 3 O 4 ferrite below and above the Verwey transition temperature. No XMCD signal has been measured in the insulating or conducting phase of Fe 3 O 4. This suggests that the absence of magnetic proximity effects at ferrite/Pt interfaces is not linked to the insulating character or not of the ferrites.
- Published
- 2017
8. Perpendicular magnetic anisotropy in granular multilayers of COPD alloyed nanoparticles
- Author
-
Matthieu Chorro, Andrei Rogalev, Adriana I. Figueroa, L. M. García, Cyrile Deranlot, Lorena Ruiz, F. Wilhelm, N. B. Brookes, Sakura Pascarelli, José F. Bartolomé, Frédéric Petroff, Javier Rubín, José M. González-Calbet, Fernando Bartolomé, L. G. Vivas, Ministerio de Economía y Competitividad (España), and Diputación General de Aragón
- Subjects
010302 applied physics ,Materials science ,Magnetic circular dichroism ,Order (ring theory) ,ComputingMilieux_LEGALASPECTSOFCOMPUTING ,02 engineering and technology ,Coercivity ,Type (model theory) ,021001 nanoscience & nanotechnology ,01 natural sciences ,Magnetic anisotropy ,Crystallography ,Ferromagnetism ,Data_GENERAL ,0103 physical sciences ,Absorption (logic) ,0210 nano-technology ,ComputingMilieux_MISCELLANEOUS ,Superparamagnetism - Abstract
Under the terms of the Creative Commons Attribution license.-- et al., Co-Pd multilayers obtained by Pd capping of pre-deposited Co nanoparticles on amorphous alumina are systematically studied by means of high-resolution transmission electron microscopy, x-ray diffraction, extended x-ray absorption fine structure, SQUID-based magnetometry, and x-ray magnetic circular dichroism. The films are formed by COPD alloyed nanoparticles self-organized across the layers, with the interspace between the nanoparticles filled by the non-alloyed Pd metal. The nanoparticles show atomic arrangements compatible with short-range chemical order of L10 strucure type. The collective magnetic behavior is that of ferromagnetically coupled particles with perpendicular magnetic anisotropy, irrespective of the amount of deposited Pd. For increasing temperature three magnetic phases are identified: hard ferromagnetic with strong coercive field, soft-ferromagnetic as in an amorphous asperomagnet, and superparamagnetic. Increasing the amount of Pd in the system leads to both magnetic hardness increment and higher transition temperatures. Magnetic total moments of 1.77(4) μB and 0.45(4) μB are found at Co and Pd sites, respectively, where the orbital moment of Co, 0.40(2) μB, is high, while that of Pd is negligible. The effective magnetic anisotropy is the largest in the capping metal series (Pd, Pt, W, Cu, Ag, Au), which is attributed to the interparticle interaction between de nanoparticles, in addition to the intraparticle anisotropy arising from hybridization between the 3d-4d bands associated to the Co and Pd chemical arrangement in a L10 structure type., The financial support of the Spanish Ministerio de Economía MAT2014-53921-R and Aragonese DGA-IMANA E34 projects is acknowledged.
- Published
- 2016
9. Magnetic tunnel junctions with monolayer hexagonal boron nitride tunnel barriers
- Author
-
Bruno Dlubak, Albert Fert, Sabina Caneva, Frédéric Petroff, John Robertson, Regina Galceran, Maëlis Piquemal-Banci, Stephan Hofmann, Abdelmadjid Anane, Marie-Blandine Martin, Piran R. Kidambi, Pierre Seneor, Karim Bouzehouane, S. Xavier, Robert S. Weatherup, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), University of Cambridge [UK] (CAM), Thales Research and Technology [Palaiseau], THALES, and Centre National de la Recherche Scientifique (CNRS)-THALES
- Subjects
[PHYS]Physics [physics] ,Materials science ,Physics and Astronomy (miscellaneous) ,Magnetoresistance ,business.industry ,Nanotechnology ,02 engineering and technology ,Chemical vapor deposition ,Nitride ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surface coating ,Tunnel magnetoresistance ,Electrical resistivity and conductivity ,Monolayer ,Optoelectronics ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,0210 nano-technology ,business ,Quantum tunnelling ,ComputingMilieux_MISCELLANEOUS - Abstract
We report on the integration of atomically thin 2D insulating hexagonal boron nitride (h-BN) tunnel barriers into Co/h-BN/Fe magnetic tunnel junctions (MTJs). The h-BN monolayer is directly grown by chemical vapor deposition on Fe. The Conductive Tip Atomic Force Microscopy (CT-AFM) measurements reveal the homogeneity of the tunnel behavior of our h-BN layers. As expected for tunneling, the resistance depends exponentially on the number of h-BN layers. The h-BN monolayer properties are also characterized through integration into complete MTJ devices. A Tunnel Magnetoresistance of up to 6% is observed for a MTJ based on a single atomically thin h-BN layer.
- Published
- 2016
10. Unveiling Self-Assembled Monolayers' Potential for Molecular Spintronics: Spin Transport at High Voltage
- Author
-
Eric Jacquet, Clément Barraud, Sergio Tatay, Albert Fert, Marta Galbiati, Pierre Seneor, Frédéric Petroff, Richard Mattana, Cyrile Deranlot, and Karim Bouzehouane
- Subjects
Materials science ,Condensed matter physics ,Spintronics ,Magnetoresistance ,Mechanical Engineering ,High voltage ,Biasing ,Self-assembled monolayer ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Tunnel magnetoresistance ,Magnetics ,Semiconductors ,Mechanics of Materials ,0103 physical sciences ,Monolayer ,Organometallic Compounds ,Nanoparticles ,General Materials Science ,Electronics ,010306 general physics ,0210 nano-technology ,Spin (physics) - Abstract
Molecular magnetic tunnel junctions using self-assembled monolayers (SAMs) as tunnel barriers show stable and efficient spin transport properties. Large tunnel magnetoresistance with a flat bias voltage dependence of the magnetoresistance is observed in La(2/3) Sr(1/3) MnO(3) /dodecylphosphonic acid SAM/Co nanocontacts. This opens the door to spintronic tailoring though SAM engineering and could also lead to new venues for spin injection in organic devices.
- Published
- 2012
- Full Text
- View/download PDF
11. Sub-nanometer Atomic Layer Deposition for Spintronics in Magnetic Tunnel Junctions Based on Graphene Spin-Filtering Membranes
- Author
-
Karim Bouzehouane, Heejun Yang, Frédéric Petroff, Bruno Dlubak, Robert S. Weatherup, Albert Fert, Abdelmadjid Anane, Stephan Hofmann, Marie-Blandine Martin, John Robertson, Cyrile Deranlot, and Pierre Seneor
- Subjects
spintronics ,Materials science ,Fabrication ,Spintronics ,Spin polarization ,Graphene ,graphene ,General Engineering ,General Physics and Astronomy ,Nanotechnology ,Dielectric ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,magnetic tunnel junction ,Article ,dielectrics ,law.invention ,Tunnel magnetoresistance ,Atomic layer deposition ,law ,Condensed Matter::Superconductivity ,atomic layer deposition ,General Materials Science ,spin filter ,Quantum tunnelling - Abstract
We report on the successful integration of low-cost, conformal, and versatile atomic layer deposited (ALD) dielectric in Ni–Al2O3–Co magnetic tunnel junctions (MTJs) where the Ni is coated with a spin-filtering graphene membrane. The ALD tunnel barriers, as thin as 0.6 nm, are grown layer-by-layer in a simple, low-vacuum, ozone-based process, which yields high-quality electron-transport barriers as revealed by tunneling characterization. Even under these relaxed conditions, including air exposure of the interfaces, a significant tunnel magnetoresistance is measured highlighting the robustness of the process. The spin-filtering effect of graphene is enhanced, leading to an almost fully inversed spin polarization for the Ni electrode of −42%. This unlocks the potential of ALD for spintronics with conformal, layer-by-layer control of tunnel barriers in magnetic tunnel junctions toward low-cost fabrication and down-scaling of tunnel resistances.
- Published
- 2014
- Full Text
- View/download PDF
12. Suppression of the critical thickness threshold for conductivity at the LaAlO3/SrTiO3 interface
- Author
-
Henri Jaffrès, Rossitza Pentcheva, Philippe Ohresser, Fadi Choueikani, Frédéric Petroff, David Doennig, Manuel Bibes, Edouard Lesne, Nicolas Reyren, Vicent Cros, Alain Barthélémy, Richard Mattana, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), and Department of Physics and Center for Nanointegration, University of Duisburg-Essen (CENIDE)
- Subjects
Multidisciplinary ,Materials science ,Condensed matter physics ,Oxide ,General Physics and Astronomy ,Nanotechnology ,Heterojunction ,02 engineering and technology ,General Chemistry ,Substrate (electronics) ,Conductivity ,Physik (inkl. Astronomie) ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Perpendicular ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,Thin film ,010306 general physics ,0210 nano-technology ,Perovskite (structure) - Abstract
International audience; Perovskite materials engineered in epitaxial heterostructures have been intensely investigated during the last decade. The interface formed by an LaAlO 3 thin film grown on top of a TiO 2-terminated SrTiO 3 substrate hosts a two-dimensional electronic system and has become the prototypical example of this field. Although controversy exists regarding some of its physical properties and their precise origin, it is universally found that conductivity only appears beyond an LaAlO 3 thickness threshold of four unit cells. Here, we experimentally demonstrate that this critical thickness can be reduced to just one unit cell when a metallic film of cobalt is deposited on top of LaAlO 3. First-principles calculations indicate that Co modifies the electrostatic boundary conditions and induces a charge transfer towards the Ti 3d bands, supporting the electrostatic origin of the electronic system at the LaAlO 3 /SrTiO 3 interface. Our results expand the interest of this low-dimensional oxide system from in-plane to perpendicular transport and to the exploration of elastic and inelastic tunnel-type transport of (spin-polarized) carriers.
- Published
- 2014
13. Negative rotatable anisotropy in IrMn/Cr/Co thin films
- Author
-
Cyrile Deranlot, Sabrina Nicolodi, Joao Edgar Schmidt, Ireth García-Aguilar, Frédéric Petroff, Narcizo M. Souza-Neto, Gustavo de Medeiros Azevedo, L. G. Pereira, A. Harres, and Julian Penkov Geshev
- Subjects
Materials science ,Condensed matter physics ,Coercivity ,Condensed Matter Physics ,Anisotropia magnética ,Ferromagnetic resonance ,Electronic, Optical and Magnetic Materials ,Transições magnéticas ,Condensed Matter::Materials Science ,Magnetization ,Magnetic anisotropy ,Nuclear magnetic resonance ,Exchange bias ,Filmes finos ,Propriedades magnéticas ,Saturation (graph theory) ,Absorption (logic) ,Anisotropy - Abstract
This work presents modifications of the magnetic properties of polycrystalline IrMn/Cr(${t}_{\mathrm{Cr}}$)/Co films where the Cr spacer thickness ${t}_{\mathrm{Cr}}$ was varied between 0.25 and 3 nm. High-resolution transmission electron microscopy, x-ray diffractometry and reflectivity, as well as x-ray absorption near-edge structure were used for the structural characterization of the films; static magnetization curves as well as ferromagnetic resonance measurements were employed for the magnetic characterization. Decrease of the exchange-bias field and considerable and nonmonotonous enhancement of the coercivity with ${t}_{\mathrm{Cr}}$ were observed. The films' anisotropy parameters were extracted from the experimental angular variations of the resonance field and from the hard-axis magnetization curves via numerical simulations. It was obtained that the two phenomena studied, namely, the exchange bias and rotatable anisotropy, have different origins. The rotatable anisotropy was ascribed to Cr interface coupled antiferromagnetically with the Co atoms. On the other hand, the occurrence of exchange bias, even for the film with the thickest Cr layer, was attributed to uncompensated spins at the topmost IrMn interface. Together with the significant increase with ${t}_{\mathrm{Cr}}$ of the rotatable anisotropy field, near saturation it is antiparallel to the external magnetic field.
- Published
- 2012
14. Breakdown of Hund's third rule in amorphous Co-W nanoparticles and crystalline Co3W alloys
- Author
-
Cyrile Deranlot, Juan Bartolomé, Andrei Rogalev, Fernando Bartolomé, F. Wilhelm, Frédéric Petroff, Luis Miguel García, Adriana I. Figueroa, Consejo Superior de Investigaciones Científicas (España), European Commission, Ministerio de Economía y Competitividad (España), and Diputación General de Aragón
- Subjects
Orientation (vector space) ,Condensed Matter::Materials Science ,Materials science ,Condensed matter physics ,Magnetic moment ,Magnetic circular dichroism ,Absorption (logic) ,Condensed Matter Physics ,Coupling (probability) ,XANES ,Spectral line ,Electronic, Optical and Magnetic Materials ,Amorphous solid - Abstract
Under the terms of the Creative Commons Attribution License 3.0 (CC-BY), We present x-ray absorption near edge structure (XANES) and x-ray magnetic circular dichroism (XMCD) measurements performed at the Co K and W L 2,3 edges, on amorphous Co-W alloy nanoparticles, and a comparison with those on a bulk Co 3W alloy. A strong hybridization between the 4p and 3d orbitals in Co and the 5d band in W are observed, resulting in an induced magnetic moment in the W atoms. The orbital to spin moment ratio in W of all these Co-W systems is positive, suggesting a parallel orientation of the two moments. This is opposite to the expected antiparallel coupling for atoms with a less-than-half-filled 5d band, according to Hund's third rule. These findings are supported by calculations of the electronic density of states projected at the Co 3d and W 5d orbitals, as well as XANES spectra and XMCD signals at the Co K and W L 2,3 edges in a Co 3W system. © 2012 American Physical Society., The financial support of the Spanish MINECO MAT2011-23791 and Aragonese DGA-IMANA (co-funded by the European Social Fund) projects is acknowledged. A.I.F. acknowledges a CSIC JAE2008-Predoc grant.
- Published
- 2012
15. Anisotropic magneto-Coulomb effect versus spin accumulation in a ferromagnetic single-electron device
- Author
-
Stéphane Fusil, Anne Bernand-Mantel, Karim Bouzehouane, Albert Fert, Frédéric Petroff, Pierre Seneor, and Cyrile Deranlot
- Subjects
Materials science ,Spintronics ,Magnetoresistance ,Condensed matter physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Coulomb blockade ,Nanoparticle ,FOS: Physical sciences ,Condensed Matter Physics ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Electronic, Optical and Magnetic Materials ,Condensed Matter::Materials Science ,Ferromagnetism ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Condensed Matter::Strongly Correlated Electrons ,Anisotropy ,Magneto ,Spin-½ - Abstract
We investigate the magnetotransport characteristics of nanospintronics single-electron devices. The devices consist of single nonmagnetic nano-objects (nanometer-size nanoparticles of Al or Cu) connected to Co ferromagnetic leads. The comparison with simulations allows us attribute the observed magnetoresistance to either spin accumulation or anisotropic magneto-Coulomb effect (AMC), two effects with very different origins. The fact that the two effects are observed in similar samples demonstrates that a careful analysis of Coulomb blockade and magnetoresistance behaviors is necessary in order to discriminate them in magnetic single-electron devices. As a tool for further studies, we propose a simple way to determine if spin transport or the AMC effect dominates from the Coulomb blockade $I$-$V$ curves of the spintronics device.
- Published
- 2011
16. Depth analysis of boron diffusion in MgO/CoFeB bilayer by x-ray photoelectron spectroscopy
- Author
-
Guy Jézéquel, Cyrile Deranlot, Aurélien Renard, Yuan Lu, Bruno Lépine, M. Alnot, Henri Jaffrès, Frédéric Petroff, J. Lambert, Martine Mullet, S. Ababou, Jean-Marie George, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), Institut Jean Lamour (IJL), Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Chimie Physique et Microbiologie pour l'Environnement (LCPME), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), THALES [France]-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
010302 applied physics ,[PHYS]Physics [physics] ,Nanostructure ,Materials science ,Annealing (metallurgy) ,Bilayer ,General Physics and Astronomy ,chemistry.chemical_element ,Heterojunction ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Crystallography ,X-ray photoelectron spectroscopy ,chemistry ,law ,0103 physical sciences ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Boron diffusion ,Crystallization ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,0210 nano-technology ,Boron - Abstract
International audience; We have studied the boron B diffusion in MgO/CoFeB bilayer by x-ray photoelectronspectroscopy depth analysis. A large concentration of B B/Mg=0.16 was found to diffuse into theMgO barrier after 350 °C annealing. The boron in MgO is in a highly oxidized B3+ state and ishomogenously distributed in the whole barrier. The important B diffusion in MgO could be relatedto the CoFeB crystallization process which begins from the under CoFeB/Ru interface and pushesboron atoms to diffuse into the MgO barrier during annealing.
- Published
- 2010
17. Structural and magnetic properties of Co-doped (La,Sr)TiO 3 epitaxial thin films probed using x-ray magnetic circular dichroism
- Author
-
Karim Bouzehouane, Abdelmadjid Anane, Vicent Cros, Rocío Ranchal, Frédéric Petroff, Karsten Rode, O. Copie, M.-A. Arrio, Manuel Bibes, Richard Mattana, N. B. Brookes, Gervasi Herranz, Eric Jacquet, Peter Bencok, Alain Barthélémy, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Trinity College Dublin, Institut de minéralogie et de physique des milieux condensés (IMPMC), Université Pierre et Marie Curie - Paris 6 (UPMC)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), European Synchrotron Radiation Facility (ESRF), THALES [France]-Centre National de la Recherche Scientifique (CNRS), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
[PHYS]Physics [physics] ,Materials science ,Absorption spectroscopy ,Magnetic circular dichroism ,Doping ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,equipment and supplies ,01 natural sciences ,Pulsed laser deposition ,X-ray magnetic circular dichroism ,chemistry ,0103 physical sciences ,General Materials Science ,Thin film ,010306 general physics ,0210 nano-technology ,Cobalt ,human activities ,Titanium - Abstract
International audience; We report a study of Co-doped La0.37Sr0.63TiO3−δ thin films grown by pulsed laser deposition in various oxygen pressure conditions. X-ray absorption spectroscopy and magnetic circular dichroism measurements at the Co L2,3 edges reveal that the cobalt mainly substitutes for the titanium and is in an ionic state. Nevertheless, in some films, indications of additional cobalt metallic impurities were found, suggesting that the intrinsic character of this magnetic system remains questionable.
- Published
- 2009
18. Spin-polarized inelastic tunneling through insulating barriers
- Author
-
Yuan Lu, H. Jaffrès, Cyrile Deranlot, Guy Jézéquel, Pierre Seneor, Frédéric Petroff, Michael Tran, J.-M. George, S. Ababou, Bruno Lépine, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Surfaces et interfaces, Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), THALES [France]-Centre National de la Recherche Scientifique (CNRS), and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Magnetoresistance ,Tunneling ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,01 natural sciences ,Variable-range hopping ,magnons ,Scattering by phonons ,Condensed Matter::Materials Science ,Theories and models ,Condensed Matter::Superconductivity ,0103 physical sciences ,73.40.Gk, 71.23.An, 72.10.Di, 72.20.Ee ,010306 general physics ,Spin (physics) ,Boron ,Quantum tunnelling ,Physics ,Condensed matter physics ,hopping transport ,Magnon ,Doping ,localized states ,021001 nanoscience & nanotechnology ,and other nonlocalized excitations ,Mobility edges ,Ferromagnetism ,chemistry ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology - Abstract
International audience; Spin-conserving hopping transport through chains of localized states has been evidenced by taking benefit of the high degree of spin-polarization of CoFeB-MgO-CoFeB magnetic tunnel junctions. In particular, our data show that relatively thick MgO barriers doped with boron favor the activation of spin-conserving inelastic channels through a chain of three localized states and leading to reduced magnetoresistance effects. We propose an extension of the Glazman-Matveev theory to the case of ferromagnetic reservoirs to account for spin-polarized inelastic tunneling through nonmagnetic localized states embedded in an insulating barrier.
- Published
- 2009
19. Engineering double-shifted hysteresis loops in Co/IrMn/Cu/Co films
- Author
-
Thiago Dias, Cyrile Deranlot, Rafael Cichelero, Julian Penkov Geshev, Frédéric Petroff, Joao Edgar Schmidt, and Luis Gustavo Pereira
- Subjects
Magnetic annealing ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Field (physics) ,Cobalto ,Chemistry ,chemistry.chemical_element ,Magnetismo ,Magnetic hysteresis ,Copper ,Ligas de manganês ,Hysteresis ,Amplitude ,Nuclear magnetic resonance ,Cobre ,Propriedades magnéticas ,Histerese magnética ,Cobalt ,Interações de troca (elétron) - Abstract
Co(3 nm)/IrMn(15 nm)/Cu(dCu)/Co(7 nm) films were subjected to magnetic annealing where its temperature and duration as well as the direction and amplitude of the applied field were varied. We demonstrate that the exchange-bias field magnitude and sign of the subloop of the bottom-pinned Co layer can be tailored in a controlled manner allowing the whole hysteresis loop to be tuned from a double negatively/negatively shifted to a double negatively/positively shifted with the shifts of the subloops in antiphase.
- Published
- 2009
20. Magnetism of 'Zn,Co...O thin films probed by x-ray absorption spectroscopies
- Author
-
J.-P. Contour, Andrei Rogalev, Frédéric Petroff, Fabrice Wilhelm, Vicent Cros, Albert Fert, Peter Bencok, Eric Jacquet, Richard Mattana, Karsten Rode, Abdelmadjid Anane, Ph. Sainctavit, N. B. Brookes, M.-A. Arrio, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Institut de minéralogie et de physique des milieux condensés (IMPMC), Université Pierre et Marie Curie - Paris 6 (UPMC)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), European Synchrotron Radiation Facility (ESRF), THALES [France]-Centre National de la Recherche Scientifique (CNRS), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,Magnetism ,Analytical chemistry ,Ionic bonding ,02 engineering and technology ,Magnetic semiconductor ,021001 nanoscience & nanotechnology ,01 natural sciences ,Condensed Matter::Materials Science ,Magnetization ,Paramagnetism ,Ferromagnetism ,0103 physical sciences ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Condensed Matter::Strongly Correlated Electrons ,Absorption (chemistry) ,Thin film ,010306 general physics ,0210 nano-technology ,human activities - Abstract
We report on the electronic and magnetic properties of Co-doped ZnO thin films investigated by x-ray absorption spectroscopies and element selective magnetometry. For a low Co concentration (around 5%), we evidence a paramagnetic phase clearly correlated to Co2+ ions substituted to Zn in the ZnO matrix. For higher Co concentrations (around 25%), we demonstrate the coexistence of both paramagnetic and ferromagnetic phases. The use of advanced element and orbital selective techniques allows us through the distinct spectral signature of Co in ionic or metallic states to assign the ferromagnetic phase to the presence of Co in a metallic state as a consequence of Co metal clustering in our films.
- Published
- 2008
21. Room temperature spin filtering in epitaxial cobalt-ferrite tunnel barriers
- Author
-
M.-J. Guittet, Frédéric Petroff, Christophe Gatel, Jean-Baptiste Moussy, Cyrile Deranlot, A. V. Ramos, and Richard Mattana
- Subjects
Spin filtering ,Condensed Matter - Materials Science ,Materials science ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Magnetoresistance ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Biasing ,Model system ,Epitaxy ,Cobalt ferrite ,Cobalt compounds ,Quantum tunnelling - Abstract
We report direct experimental evidence of room temperature spin filtering in magnetic tunnel junctions (MTJs) containing CoFe2O4 tunnel barriers via tunneling magnetoresistance (TMR) measurements. Pt(111)/CoFe2O4(111)/gamma-Al2O3(111)/Co(0001) fully epitaxial MTJs were grown in order to obtain a high quality system, capable of functioning at room temperature. Spin polarized transport measurements reveal significant TMR values of -18% at 2 K and -3% at 290 K. In addition, the TMR ratio follows a unique bias voltage dependence that has been theoretically predicted to be the signature of spin filtering in MTJs containing magnetic barriers. CoFe2O4 tunnel barriers therefore provide a model system to investigate spin filtering in a wide range of temperatures., 6 pages, 3 figures
- Published
- 2007
22. Layer-resolved imaging of domain wall interactions in magnetic tunnel junction-like trilayers
- Author
-
Andrea Locatelli, Julio Camarero, Frédéric Petroff, Stefania Pizzini, Salia Cherifi, Fabien Romanens, Jan Vogel, Stefan Heun, Micro et NanoMagnétisme (MNM), Institut Néel (NEEL), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS), Departamento de Fisica de la Materia Condensada [Madrid] (FMC), Facultad de Ciencas [Madrid], Universidad Autonoma de Madrid (UAM)-Universidad Autonoma de Madrid (UAM), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), Laboratorio Nazionale TASC (TASC), Consiglio Nazionale delle Ricerche [Roma] (CNR)-INFM, Elettra Sincrotrone Trieste, Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), and Centre National de la Recherche Scientifique (CNRS)-THALES
- Subjects
DYNAMICS ,Materials science ,magnetic imaging ,FOS: Physical sciences ,magnetization dynamics ,02 engineering and technology ,magnetic domains ,01 natural sciences ,PHOTOEMISSION ELECTRON-MICROSCOPY ,INTERLAYER EXCHANGE ,Magnetization ,Condensed Matter::Materials Science ,XMCD-PEEM ,0103 physical sciences ,General Materials Science ,010306 general physics ,Anisotropy ,Condensed matter physics ,SUPERLATTICES ,domain walls ,75.60.Ch, 75.70.Kw, 07.85.Tt ,GIANT MAGNETORESISTANCE ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Condensed Matter - Other Condensed Matter ,Tunnel magnetoresistance ,Photoemission electron microscopy ,[PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other] ,0210 nano-technology ,Antiparallel (electronics) ,Other Condensed Matter (cond-mat.other) - Abstract
We have performed a layer-resolved, microscopic study of interactions between domain walls in two magnetic layers separated by a non-magnetic one, using high-resolution x-ray photoemission electron microscopy. Domain walls in the hard magnetic Co layer of a Co/Al2O3/FeNi trilayer with in-plane uniaxial anisotropy strongly modify the local magnetization direction in the soft magnetic FeNi layer. The stray fields associated to the domain walls lead to an antiparallel coupling between the local Co and FeNi moments. For domain walls parallel to the easy magnetization axis this interaction is limited to the domain wall region itself. For strongly charged (head-on or tail-to-tail) walls, the antiparallel coupling dominates the interaction over radial distances up to several micrometers from the centre of the domain wall., Comment: Published version, J. Phys.: Condens. Matter 19, 476204 (2007)
- Published
- 2007
23. Magnetoresistance and spin electronics
- Author
-
Frédéric Petroff, J.-P. Contour, Martin Bowen, J. C. Faini, J. M. De Teresa, F. Pailloux, Vicent Cros, Albert Fert, J.-M. George, Amir Hamzić, Julie Grollier, Alain Barthélémy, C. Vouille, and François Montaigne
- Subjects
Spin pumping ,Materials science ,Condensed matter physics ,Spintronics ,Spin polarization ,Magnetoresistance ,Giant magnetoresistance ,Spin polarized scanning tunneling microscopy ,Condensed Matter Physics ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Electronic, Optical and Magnetic Materials ,Tunnel magnetoresistance ,Condensed Matter::Materials Science ,Tunnel junction ,Condensed Matter::Superconductivity ,Condensed Matter::Strongly Correlated Electrons ,Spin injection ,Tunnel junctions - Abstract
We review several topics in the field of spin electronics: (i) giant magnetoresistance observed in magnetic multilayers; (ii) magnetization reversal by spin injection and (iii) spin-polarized tunneling in magnetic tunnel junctions combining electrodes of ferromagnetic transition metal and half-metallic oxide.
- Published
- 2002
24. Magnetism of the Fe/ZnSe(001) interface
- Author
-
Ph. Sainctavit, Peter Bencok, N. B. Brookes, M. Eddrief, Fredrik Gustavsson, Frédéric Petroff, Massimiliano Marangolo, Victor H. Etgens, Vicent Cros, J.-M. George, Laboratoire de minéralogie, cristallographie de Paris (LMCP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), and Université Pierre et Marie Curie - Paris 6 (UPMC)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Materials science ,Magnetoresistance ,Magnetism ,75.70.Cn, 68.37.-d, 75.70.Rf ,General Physics and Astronomy ,02 engineering and technology ,01 natural sciences ,magnetic epitaxial layers ,Condensed Matter::Materials Science ,iron ,interface magnetism ,0103 physical sciences ,ferromagnetic materials ,010306 general physics ,Magnetic moment ,Spintronics ,Condensed matter physics ,local moments ,Condensed Matter::Other ,Heterojunction ,II-VI semiconductors ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,metallic epitaxial layers ,Magnetic anisotropy ,Ferromagnetism ,annealing ,0210 nano-technology ,zinc compounds ,Molecular beam epitaxy ,magnetic circular dichroism - Abstract
In the present thesis, the properties at ferromagnet/semiconductor interfaces, relevant for semiconductor spintronics applications, are addressed. Semiconductor spintronics refers to the possibility of storing information using the electron spin, additional to the electron charge, for enhanced flexibility in nanoscale semiconductor devices. The system under focus is the Fe/ZnSe(001) heterostructure, where ZnSe is a wide gap semiconductor ideally compatible with GaAs. The heterostructures are grown on GaAs(001) substrates by molecular beam epitaxy. From various electron-beam based diffraction, spectroscopy and microscopy techniques, it is shown that Fe grows epitaxially and predominantly in a layer-by-layer mode on ZnSe(001) with no presence of chemically reacted phases or interdiffusion. An in-plane uniaxial magnetic anisotropy (UMA) is detected for thin Fe films on ZnSe(001) by magnetometry, thus opposing the cubic symmetry of bcc Fe. From first principles calculations, the unidirectional sp3-bonds from ZnSe are shown to induce this uniaxiality. Moreover, an in-plane anisotropic lattice relaxation of Fe is found experimentally, seemingly as a consequence of the sp3-bonds, giving an additional UMA contribution via magneto-elastic coupling. It is proposed that these two effects are responsible for the much-debated UMA observed in Fe/semiconductor structures in general. The interface magnetism is probed by x-ray magnetic circular dichroism and Mossbauer spectroscopy. It is found that the magnetic moment at the interface is comparable or even enhanced with respect to the bulk Fe. These two experiments are believed to provide the first unambiguous proof of a persistent bulk magnetic moment at a transition metal/semiconductor interface. Spin-polarised transport measurements are performed on Fe/ZnSe/FeCo magnetic tunnel junctions. A magnetoresistance of 16% is found at low temperature, which evidences both the existence of interface spin polarisation, as inferred from the bulk magnetic moment above, and that the spin polarisation can be transmitted across the semiconductor barrier layer.
- Published
- 2002
25. Enhancement of the magnetic anisotropy of nanometer-sized Co clusters: influence of the surface and of the inter-particle interactions
- Author
-
A. Vaures, Jean-Luc Maurice, Fernando Luis, Jeremie Torres, Frédéric Petroff, Jolanta Stankiewicz, Javier Bartolomé, F. Fettar, Luis Miguel García, Comisión Interministerial de Ciencia y Tecnología, CICYT (España), and European Commission
- Subjects
Magnetization ,Magnetic anisotropy ,Condensed Matter - Materials Science ,Materials science ,Magnetic moment ,Condensed matter physics ,Sputtering ,Particle-size distribution ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Activation energy ,Anisotropy ,Scaling - Abstract
We study the magnetic properties of spherical Co clusters with diameters between 0.8 nm and 5.2 nm (25–7000 atoms) prepared by sequential sputtering of Co and Al2O3. The particle size distribution has been determined from the equilibrium susceptibility and magnetization data and it is compared with previous structural characterizations. The distribution of activation energies has been independently obtained from a scaling plot of the ac susceptibility. Combining these two distributions we have accurately determined the effective anisotropy constant Keff. We find that Keff is enhanced with respect to the bulk value and that it is dominated by a strong anisotropy induced at the surface of the clusters. Interactions between the magnetic moments of adjacent layers are shown to increase the effective activation energy barrier for the reversal of the magnetic moments. Finally, this reversal process is shown to proceed classically down to the lowest temperature investigated (1.8 K)., This work has been partly funded by Spanish Grant No. MAT 99/1142 and the European ESPRIT contract ‘‘MASSDOTS.’’
- Published
- 2001
26. Review of recent results on spin polarized tunneling and magnetic switching by spin injection
- Author
-
Vicent Cros, F. Pailloux, J.-P. Contour, Julie Grollier, Frédéric Petroff, J. M. De Teresa, J.-M. George, Giancarlo Faini, François Montaigne, Henri Jaffrès, Alain Barthélémy, J. Ben Youssef, Albert Fert, Amir Hamzić, and H. Le Gall
- Subjects
Spin pumping ,Materials science ,Condensed matter physics ,Spin polarization ,tunnel magnetoresistance ,magnetization reversal ,spin injection ,Co/Cu/Co trilayers ,Mechanical Engineering ,Spin polarized scanning tunneling microscopy ,Condensed Matter Physics ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter::Materials Science ,Transition metal ,Mechanics of Materials ,Tunnel junction ,Condensed Matter::Superconductivity ,Spin Hall effect ,Spinplasmonics ,General Materials Science ,Condensed Matter::Strongly Correlated Electrons ,Spin-½ - Abstract
We review recent results obtained at Orsay on two topics in the field of spin electronics: (i) Spin polarized tunneling in magnetic tunnel junctions combining electrodes of ferromagnetic transition metal and half-metallic oxide: we will describe the influence of the nature of the barrier on the sign of the spin polarization of electrons tunneling from the transition metal and we also discuss the temperature dependence of the TMR obtained with half metallic oxides. (ii) Magnetization reversal by spin injection: we will present and interpret experimental results obtained with pillar-shaped Co/Cu/Co trilayers.
- Published
- 2001
27. Reduced magnetic moment per atom in small Ni and Co clusters embedded in AlN
- Author
-
Agnès Traverse, C. Clerc, Frédéric Petroff, C.M. Teodorescu, Hélène Fischer, C. Bellouard, C. Pélissier, Didier Zanghi, 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), Laboratoire pour l'utilisation du rayonnement électromagnétique (LURE), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-MENRT-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), Laboratoire de physique des matériaux (LPM), Université Henri Poincaré - Nancy 1 (UHP)-Institut National Polytechnique de Lorraine (INPL)-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), THALES-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique de Lorraine (INPL)-Université Henri Poincaré - Nancy 1 (UHP)
- Subjects
010302 applied physics ,Materials science ,Magnetic moment ,Magnetic circular dichroism ,Analytical chemistry ,General Physics and Astronomy ,Sputter deposition ,01 natural sciences ,law.invention ,SQUID ,Ion implantation ,Ferromagnetism ,law ,0103 physical sciences ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Cluster (physics) ,Magnetic nanoparticles ,[PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det] ,010306 general physics ,ComputingMilieux_MISCELLANEOUS - Abstract
Nanoparticles of cobalt and nickel embedded in AlN matrix have been prepared by ion implantation or sputter deposition with average diameters ranging from 0.8 to 9 nm. The average magnetic moment per atom versus the average cluster diameter was measured either by x-ray magnetic circular dichroism and/or by SQUID magnetometry. The resulting values are always smaller than the bulk ones. An interpretation is given in terms of an interaction between the atoms located at the cluster surface and the AlN matrix, leading to a magnetically dead layer about 0.1 nm thick.
- Published
- 2001
28. Giant magnetoresistance of (001)fe/(001)cr magnetic superlattices
- Author
-
J. M. Broto, P. Etienne, Jean Chazelas, A. Friederich, Albert Fert, G. Creuzet, F. Nguyen Van Dau, Mario Norberto Baibich, and Frédéric Petroff
- Subjects
Materials science ,Materiais magnéticos ,Condensed matter physics ,Magnetoresistance ,Superlattice ,General Physics and Astronomy ,Propriedades eletronicas, magneticas e termodinamicas dos solidos ,Giant magnetoresistance ,Electron ,Epitaxy ,Thermal conduction ,Magnetic field ,Electrical resistivity and conductivity ,Super-redes - Abstract
We have studied the magnetoresistance of (001)Fe/(001)Cr superlattices prepared by molecularbeam epitaxy. A huge magnetoresistance is found in superlattices with thin Cr layers: For example, with ${t}_{\mathrm{Cr}}=9$ \AA{}, at $T=4.2$ K, the resistivity is lowered by almost a factor of 2 in a magnetic field of 2 T. We ascribe this giant magnetoresistance to spin-dependent transmission of the conduction electrons between Fe layers through Cr layers.
- Published
- 1988
29. Molecular spintronics: the role of spin-dependent hybridization.
- Author
-
Sophie Delprat, Marta Galbiati, Sergio Tatay, Benoît Quinard, Clément Barraud, Frédéric Petroff, Pierre Seneor, and Richard Mattana
- Subjects
SPINTRONICS ,FERROMAGNETISM ,MAGNETORESISTIVE devices - Abstract
Spin-dependent hybridization at the ferromagnet/molecule interface has recently unveiled a promising new potential for spintronics. By projecting the spintronic properties (i.e. induced spin polarization) from a given ferromagnet electrode to the highly versatile and tailorable molecular layer, spin-dependent hybridization has opened up new opportunities to tailor spintronic device properties at the molecular scale. Here we focus on the potential and impact of this hybridization on spintronic devices. Depending on the coupling strength at the ferromagnet/molecule interface, the induced spin polarization can be enhanced or even inversed. In the first part of the paper, we introduce the concept of spin-dependent hybridization and, in particular, we show that it allows the magnetoresistive response of spintronic devices to be tuned. In the second part, we review the experimental evidence emphasizing spin-dependent hybridization in molecular layers and single molecules. In the last part, we highlight how this spin-dependent hybridization can play a key role in tunnelling magnetoresistance and tunnelling anisotropic magnetoresistance. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
30. Atomic layer deposition of a MgO barrier for a passivated black phosphorus spintronics platform
- Author
-
Pierre Brus, Bernard Servet, Marta Galbiati, Florian Godel, M. Martin, Pierre Seneor, Frédéric Petroff, Etienne Gaufrès, Bruno Dlubak, David Perconte, Odile Bezencenet, Regina Galceran, L.-M. Kern, Annick Loiseau, F. Bouamrane, Victor Zatko, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Laboratoire d'étude des microstructures [Châtillon] (LEM - ONERA - CNRS), Centre National de la Recherche Scientifique (CNRS)-ONERA, DMAS, ONERA, Université Paris Saclay (COmUE) [Châtillon], ONERA-Université Paris Saclay (COmUE), Thales Research and Technology [Palaiseau], and THALES
- Subjects
010302 applied physics ,Materials science ,Fabrication ,Physics and Astronomy (miscellaneous) ,Passivation ,Spintronics ,business.industry ,Nucleation ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Espectroscòpia Raman ,Atomic layer deposition ,0103 physical sciences ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Optoelectronics ,Thin film ,0210 nano-technology ,business ,Layer (electronics) ,Materials ,Quantum tunnelling - Abstract
International audience; We demonstrate a stabilized black phosphorus (BP) 2D platform thanks to an ultrathin MgO barrier, as required for spintronic device integration. The in-situ MgO layer deposition is achieved by using a large-scale atomic layer deposition process with high nucleation density. Raman spectroscopy studies show that this layer protects the BP from degradation in ambient conditions, unlocking in particular the possibility to carry out usual lithographic fabrication steps. The resulting MgO/BP stack is then integrated in a device and probed electrically, confirming the tunnel properties of the ultrathin MgO contacts. We believe that this demonstration of a BP material platform passivated with a functional MgO tunnel barrier provides a promising perspective for BP spin transport devices.
- Full Text
- View/download PDF
31. Self-assembled monolayers based spintronics: from ferromagnetic surface functionalization to spin-dependent transport.
- Author
-
Sergio Tatay, Marta Galbiati, Sophie Delprat, Clément Barraud, Karim Bouzehouane, Sophie Collin, Cyrile Deranlot, Eric Jacquet, Pierre Seneor, Richard Mattana, and Frédéric Petroff
- Published
- 2016
- Full Text
- View/download PDF
32. Spintronique moléculaire : des semi-conducteurs organiques aux monocouches auto-assemblées
- Author
-
Galbiati, Marta, Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), Université Paris Sud - Paris XI, Frédéric Petroff, and Pierre Seneor
- Subjects
Molecular spintronics ,Organic semiconductors ,Semi-conducteurs organiques ,[PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other] ,Monocouches auto-assemblées ,Self-assembled monolayers ,Spintronique moléculaire - Abstract
This thesis targets the field of molecular spintronics and more particularly the new spin polarization tailoring opportunities, unachievable with inorganic materials, which arise from the ferromagnetic metal/molecule hybridization at the interface.: the new concept of Spinterface.In a first part we investigate Self-Assembled Monolayers (SAMs) based magnetic tunnel nanojunctions. This system appears to be a highly promising candidate to engineer the properties of spintronics devices at the molecular level since SAMs are the equivalent of a molecular LEGO building unit. We present the functionalization of the half-metallic manganite (La,Sr)MnO3 (LSMO) with alkyl phosphonic acids SAMs and the fabrication of LSMO/SAMs/Co magnetic tunnel nanojunctions with an area of few 10 nm2. MR of 30% to 50% is observed in most of the devices, while we report even up to 250% tunnel magnetoresistance (TMR) at low temperature. The most striking point is the robustness of the signal with bias voltage with still 20% TMR observed in the volt range. The influence of the molecular chain length is also investigated and represents a first step towards achieving molecular tailoring.In a second part we develop organic spintronics devices relying on high Curie temperature metallic ferromagnetic electrodes and standard organic semiconductor such as Co/Alq3/Co organic spin valves (OSVs). Junctions have a large area (section of 50 or 100 µm) and are fabricated in-situ by shadow mask. Magnetoresistance (MR) effects at room temperature are investigated with -4% MR observed in Co/Alq3/Co OSVs and +8% MR in Co/MgO/Alq3/Co OSVs. The role of the two interfaces on the spin polarization properties of the devices is also investigated. A stronger spin-dependent hybridization is found to occur at the bottom Co/Alq3 interface inverting the spin polarization on the first molecular layer. The observation of spin polarization inversion at room temperature demonstrates that spinterface effects can strive up to room temperature.; Cette thèse s’inscrit dans le domaine de la spintronique moléculaire. Elle s’intéresse plus précisément aux nouvelles opportunités de façonnage de la polarisation de spin qui découlent de l'hybridation métal ferromagnétique/molécule à l'interface : le nouveau concept de « spinterface ».Dans une première partie nous présentons l’étude de nanojonctions tunnel magnétiques à base de monocouches auto-assemblées (SAMs). Ce système est un des plus prometteur dans l’optique de moduler les propriétés des dispositifs de spintronique par ingénierie chimique, tel un LEGO moléculaire. Nous y présentons la fonctionnalisation de la manganite demi-métallique (La,Sr)MnO3 (LSMO) avec des SAMs d’acides alkylphosphoniques et la fabrication de nanojonctions LSMO/SAMs/Co avec une surface de quelque 10 nm2. Une magnétorésistance de 30% à 50% est observée dans la majorité des dispositifs avec une magnétorésistance tunnel (TMR) jusqu'à 250 % à basse température. Un point remarquable est aussi le comportement très robuste du signal avec la tension: environ 20% de TMR est encore observée au-dessus d’une tension de 1 V. L'influence de la longueur de la chaîne moléculaire a été aussi étudiée et représente un premier pas vers la modulation des dispositifs au niveau moléculaire. Dans une deuxième partie nous présentons l’étude des dispositifs organiques à base de métaux ferromagnétiques à haute TC (température de Curie) et semi-conducteurs organiques. Nous avons réalisé des vannes de spin de Co/Alq3/Co avec des sections de 50 ou 100 µm et fabriquées in-situ par « shadow mask ». Des mesures à température ambiante ont permis d’observer -4% de magnétorésistance (MR) dans une vanne de spin Co/Alq3/Co et +8% MR dans une vanne de spin de Co/MgO/Alq3/Co. Le rôle des deux interfaces sur les propriétés de polarisation de spin des dispositifs est aussi étudié et détaillé. Une forte hybridation métal/molécule dépendant du spin à l'interface inferieure de Co/Alq3, présentant un effet de spinterface (inversion de la polarisation en spin), est observée. Ces études montrent que les effets de spinterface, comme l’inversion de la polarisation de spin, peuvent persister dans un dispositif jusqu’à température ambiante.
- Published
- 2014
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.