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George Kastrinakis - One of the best experts on this subject based on the ideXlab platform.

  • Paramagnons, weak disorder and positive Giant Magnetoresistance
    Europhysics Letters (EPL), 1998
    Co-Authors: George Kastrinakis
    Abstract:

    At low temperature and for finite spin scattering in a weakly disordered metal, for a certain value, predicted from our theory, of the material-dependent paramagnon interaction, the total conductivity becomes highly sensitive to the orbital effects of a finite magnetic field. As a consequence, positive Giant Magnetoresistance and Giant corrections to the Hall coefficient arise. We obtain very good agreement between this theory and recent positive Giant Magnetoresistance experiments.

  • Paramagnons, weak disorder and positive Giant Magnetoresistance
    arXiv: Disordered Systems and Neural Networks, 1995
    Co-Authors: George Kastrinakis
    Abstract:

    At low temperature and for finite spin scattering in a weakly disordered metal, for a certain value, predicted from our theory, of the material-dependent paramagnon interaction, the total conductivity becomes highly sensitive to the orbital effects of a finite magnetic field. As a consequence, positive Giant Magnetoresistance and Giant corrections to the Hall coefficient arise. We obtain very good agreement between this theory and recent positive Giant Magnetoresistance experiments, while making specific material-dependent predictions.

Bernard Dieny - One of the best experts on this subject based on the ideXlab platform.

  • Quantum statistical theory of Giant Magnetoresistance in magnetic heterogeneous alloys
    Journal of Magnetism and Magnetic Materials, 1996
    Co-Authors: A.v. Vedyayev, Bernard Dieny, A. Chamberod, B. Mevel, N.v. Ryzhanova, M. Tshiev, François Brouers
    Abstract:

    Abstract We present a quantum-statistical theory of Giant Magnetoresistance in magnetic heterogeneous alloys, consisting of small particles of ferromagnetic metal embedded in a nonmagnetic conducting matrix. The paper focuses on the spin-dependent size-effect on the conductivity of the system, i.e. the influence of the relative orientation of the magnetization in neighboring particles on their conductivity as a function of the size and distance between the particles. It is shown that the conductivity of heterogeneous alloys is not self-averaging when the particle sizes and/or distances are comparable to the mean-free paths. As for current in-plane Giant Magnetoresistance, the electron mean-free paths are the relevant length scale parameters. When the size-effects due to the bulk and interfacial spin-dependent electron scattering are taken into account, the Giant Magnetoresistance amplitude exhibits a maximum as a function of the average radius of the particles. The optimum radius value is determined by a balance between the interfacial and bulk scattering.

  • Giant Magnetoresistance in spin valve multilayers
    Journal of Magnetism and Magnetic Materials, 1994
    Co-Authors: Bernard Dieny
    Abstract:

    Abstract A comprehensive review of Giant Magnetoresistance in spin-valve sandwiches and multilayers is presented, highlighting the experimental and theoretical results which are of particular interest for the development of applications of these systems, especially in magnetic recording technology. The main points discussed include the physical origin of the Giant Magnetoresistance, the influence of the thicknesses of the magnetic and nonmagnetic layers, the influence of the interfacial roughness, the angular dependence of the Giant Magnetoresistance, and the ability to obtain linear R ( H ) characteristics. A summary of the properties of some systems among the most promising for low-field applications is given. Some theoretical results, based on an extension to Camley and Barnas's semi-classical theory, are presented. This simple theoretical approach can serve as a tool in the optimization of the thicknesses or number of periods of spin-valve structures.

  • Giant Magnetoresistance in melt-spun metallic ribbons
    Journal of Magnetism and Magnetic Materials, 1994
    Co-Authors: Bernard Dieny, A. Chamberod, C. Cowache, J.b. Genin, S. R. Teixeira, R. Ferré, Bernard Barbara
    Abstract:

    Abstract We report the observation of Giant Magnetoresistance in as-quenched and annealed metallic ribbons prepared by melt-spinning in an argon atmosphere. The samples consist of heterogeneous Co x Cu 1− x alloys with x varying between 5 and 30%. A Magnetoresistance of the order of 20% in 50 kOe at 5 K is obtained in these samples after optimized annealing. The amplitude of this Magnetoresistance is similar to that obtained in sputtered samples of the same composition. In contrast to techniques of thin-film growth (sputtering, UHV evaporation, MBE), this method of preparation allows for the production of a large quantity of material exhibiting Giant Magnetoresistance in the form of ribbons or wires which are a few tens of microns thick, a few millimeters wide and tens of meters long.

  • Role of interfacial mixing in Giant Magnetoresistance.
    Physical review. B Condensed matter, 1993
    Co-Authors: Virgil Simon Speriosu, Bernard Dieny, J.‐p. Nozieres, B.a. Gurney, T. C. Huang, H. Lefakis
    Abstract:

    We show that the Giant Magnetoresistance in sputtered Ni-Fe/Cu/Ni-Fe/Fe-Mn spin-valve structures is strongly reduced by the presence of compositionally intermixed regions at the NiFe/Cu interfaces. The ultrathin intermixed layers, which are not ferromagnetic, are centers of strong spin-independent scattering, thus reducing the flow of polarized electrons from one ferromagnetic layer to the other. Our results show that interfacial spin-independent scattering must be included in the theory of Giant Magnetoresistance

L. B. Steren - One of the best experts on this subject based on the ideXlab platform.

  • Giant Magnetoresistance in oxide-based metallic multilayers
    Applied Physics Letters, 2007
    Co-Authors: M. Granada, J. Carlos Rojas Sánchez, L. B. Steren
    Abstract:

    The authors report on the first measurement of low-field Giant Magnetoresistance in metallic multilayers of perovskite oxides. The authors performed in-plane measurements of the magnetoelectric transport properties in La0.75Sr0.25MnO3∕LaNiO3 trilayers and succeeded in distinguishing the Giant Magnetoresistance effect from other contributions to the total Magnetoresistance. The samples were grown on single-crystalline SrTiO3 substrates by dc sputtering.

  • Giant Magnetoresistance in hybrid magnetic nanostructures
    Journal of Magnetism and Magnetic Materials, 1995
    Co-Authors: L. B. Steren, Agnès Barthélémy, Albert Fert, R. Morel, Frédéric Petroff, P. Holody, Reza Loloee, Peter A. Schroeder
    Abstract:

    Abstract We report on magnetization and Magnetoresistance measurements in hybrid structures, composed of soft magnetic layers of permalloy and hard magnetic clustered-layers of cobalt separated by silver. We also present a study of the dependence of the Giant Magnetoresistance effect with the angle between the magnetizations of successive magnetic layers.

  • Giant Magnetoresistance in magnetic nanostructures
    Nanostructured Materials, 1995
    Co-Authors: Agnès Barthélémy, Vincent Cros, Jean-luc Duvail, Albert Fert, R. Morel, F. Parent, Frédéric Petroff, L. B. Steren
    Abstract:

    Abstract Since its discovery in magnetic multilayers, the Giant Magnetoresistance has become one major research topic in both applied and pure magnetism. At first, new theories had to be devised to explain the oscillating indirect exchange coupling and to understand how spin-dependent transport properties give rise to the Giant Magnetoresistance. Also, because the magnetic multilayer where, at the time, a new class of materials, a lot of attention has been devoted to the study of their structural properties. In this paper, we review some experimental results and theoretical models on GMR in magnetic multilayers. Then, we present an overview of the Giant Magnetoresistance in new nanostructures - granular alloys and hybrid systems - with magnetic entities in the form of clusters instead of layers.

  • Giant Magnetoresistance in hybrid nanostructures
    Journal of Magnetism and Magnetic Materials, 1995
    Co-Authors: Jean-luc Duvail, Agnès Barthélémy, Albert Fert, R. Morel, Frédéric Petroff, L. B. Steren, P. Holody, M. Sussiau, M. Wiedmann, Reza Loloee
    Abstract:

    Abstract We describe the Giant Magnetoresistance (GMR) properties of multilayered structures including continuous layers of permalloy (Ni80Fe20) and discontinuous layers of cobalt separated by layers of copper or silver. These hybrid structures exhibit large GMR ratios with high slopes at low field (as high as 7%/Oe). They are also very convenient for an accurate determination of the angular dependence of the GMR and interesting to discuss the origin of the GMR. We finally analyse GMR measurements performed with the current perpendicular to the layers and separate the bulk and interface contributions.

Gerrit E. W. Bauer - One of the best experts on this subject based on the ideXlab platform.

  • Ballistic Giant Magnetoresistance
    Journal of Magnetism and Magnetic Materials, 1996
    Co-Authors: Kees M. Schep, Paul J. Kelly, Gerrit E. W. Bauer
    Abstract:

    Abstract We present a theoretical study of the Giant Magnetoresistance in the ballistic regime for Co/Cu and Fe/Cr multilayers which emphasizes the importance of band structure effects, both for the perpendicular (CPP) and the parallel (CIP) geometry.

  • Giant Magnetoresistance from first principles
    Journal of Magnetism and Magnetic Materials, 1995
    Co-Authors: Kees M. Schep, Paul J. Kelly, Gerrit E. W. Bauer
    Abstract:

    Abstract The transport properties of Co/Cu multilayers are calculated from first principles in the ballistic regime. Magnetoresistances as large as 120% are obtained in the geometry with the current perpendicular to the interface plane. The s-d hybridization is found to play an essential role in giving rise to this Giant Magnetoresistance effect.

  • Giant Magnetoresistance and electronic structure
    MRS Proceedings, 1995
    Co-Authors: Kees M. Schep, Paul J. Kelly, Gerrit E. W. Bauer
    Abstract:

    ABSTRACTThe electronic structure of magnetic multilayers is expected to play an important role in determining their transport properties. We explain how the conductance through a ballistic point contact is related to simple geometrical projections of the Fermi surface. The essential physics is first discussed for simple model systems and then realistic results for magnetic metallic multilayers based on first principles band structure calculations are presented. The electronic structure is shown to make an important contribution to the perpendicular Giant Magnetoresistance.

  • Mesoscopic aspects of the Giant Magnetoresistance
    Journal of Magnetism and Magnetic Materials, 1995
    Co-Authors: Gerrit E. W. Bauer, Kees M. Schep, Paul J. Kelly
    Abstract:

    Abstract Microscopic information about electron scattering at heterointerfaces which is relevant for the Giant Magnetoresistance (GMR) in metallic multilayers can be obtained from measurements carried out in the mesoscopic regime. First-principles calculations of transport through ballistic multilayers demonstrate the importance of taking into account the complicated band structure. The statistics of transport through single disordered interfaces is shown to be non-universal, which means that the fluctuation properties can yield new information on the interface disorder scattering.

K.-m. H. Lenssen - One of the best experts on this subject based on the ideXlab platform.

  • Robust Giant Magnetoresistance sensors
    Sensors and Actuators A-physical, 2000
    Co-Authors: K.-m. H. Lenssen, Derk J. Adelerhof, H.j Gassen, Antonius E. T. Kuiper, Gerardus H. J. Somers, J.b.a. Van Zon
    Abstract:

    Abstract The Giant Magnetoresistance (GMR) effect offers interesting new possibilities for sensor applications. A short overview is given of the GMR effect in relation to its application in (automotive and industrial) field sensors. In the past the thermal and magnetic stability could not fulfil the requirements for use in automotive and industrial environments. Recently, a new, robust GMR material system has been developed that can withstand high temperatures (>200°C) and large magnetic fields (>200 kA/m). Using this material, GMR sensor elements have been fabricated and measured. Moreover, preliminary measurements on the first robust GMR sensor with a full Wheatstone-bridge configuration will be presented.

  • Giant Magnetoresistance MATERIALS FOR READ HEADS
    Philips Journal of Research, 1998
    Co-Authors: R Reinder Coehoorn, J.c.s. Kools, Th. G. S. M. Rijks, K.-m. H. Lenssen
    Abstract:

    The sensitivity of magnetoresistive read heads can be increased by using layered magnetic materials showing the Giant Magnetoresistance effect, instead of a single magnetic film showing the anisotropic Magnetoresistance effect. For this purpose, exchange-biased spin-valve layered structures are very suitable. For well-chosen compositions and nanometer-scale layer thicknesses these materials combine a fair Giant Magnetoresistance effect with a very small field interval in which the resistance change takes place. In this paper we give an overview of aspects which determine the functioning of materials of this class in read heads, including their preparation, magnetotransport properties and the magnetic interactions which determine the magnetization reversal process.