The Present and the Future of Spintronics

The article describes the development of spintronics from the first studies of spin dependent transport in ferromagnetic materials to the discovery of the giant magnetoresistance and to the most recent advances

Advances in the Physics of Magnetic Skyrmions and Perspective for Technology

Magnetic skyrmions are small swirling topological defects in the magnetization texture stabilized by the protection due to their topology. In most cases they are induced by chiral interactions between atomic spins existing in non-centrosymmetric magnetic compounds or in thin films in which inversion symmetry is broken by the presence of an interface. The skyrmions can be extremely small with diameters in the nanometer range and, importantly, they behave as particles that can be moved, created or annihilated, making them suitable for abacus-type applications in information storage, logic or neuro-inspired technologies. Up to the last years skyrmions were observed only at low temperature (and in most cases under large applied fields) but important efforts of research has been recently devoted to find thin film and multilayered structures in which skyrmions are stabilized above room temperature and manipulated by current. This article focuses on these recent advances on the route to devices prototypes.Comment: Published online 13 June 2017 : 17 pages, 8 figures and 2 boxe

Spintronique, de la magnétorésistance géante aux Skyrmions magnétiques et isolants topologiques

International audienceThis article aims at giving a general presentation of spintronics, an important field of research developing today along many new directions in physics of condensed matter. We tried to present simply the physical phenomena involved in spintronics – no equations but many schematics. We also described the applications of spintronics, those of today and those expected to have an important impact on the next developments of the information and communication technologies.Cet article se veut une présentation générale de la spintronique. C’est aujourd’hui un important domaine de recherche qui se développe sur de nombreux nouveaux axes de la physique de la matière condensée. Nous avons voulu présenter simplement les phénomènes physiques impliqués dans la spintronique – sans équations mais avec de nombreux schémas. Nous décrivons aussi les applications de la spintronique, celles d’aujourd’hui et celles dont l’on attend un impact important sur les prochains développements des technologies de l’information et de la communication

Spin torque and waviness in magnetic multilayers: a bridge between Valet-Fert theory and quantum approaches

We develop a simple theoretical framework for transport in magnetic multilayers, based on Landauer-Buttiker scattering formalism and Random Matrix Theory. A simple transformation allows one to go from the scattering point of view to theories expressed in terms of local currents and electrochemical potential. In particular, our theory can be mapped onto the well established classical Valet Fert theory for collinear systems. For non collinear systems, in the absence of spin-flip scattering, our theory can be mapped onto the generalized circuit theory. We apply our theory to the angular dependance of spin accumulation and spin torque in non-collinear spin valves

Electrical signature of individual magnetic skyrmions in multilayered systems

Magnetic skyrmions are topologically protected whirling spin textures that can be stabilized in magnetic materials in which a chiral interaction is present. Their limited size together with their robustness against the external perturbations promote them as the ultimate magnetic storage bit in a novel generation of memory and logic devices. Despite many examples of the signature of magnetic skyrmions in the electrical signal, only low temperature measurements, mainly in magnetic materials with B20 crystal structure, have demonstrated the skyrmions contribution to the electrical transport properties. Using the combination of Magnetic Force Microscopy (MFM) and Hall resistivity measurements, we demonstrate the electrical detection of sub-100 nm skyrmions in multilayered thin film at room temperature (RT). We furthermore analyse the room temperature Hall signal of a single skyrmion which contribution is mainly dominated by anomalous Hall effect.Comment: 13 pages, 4 figure

Influence Of Current Leads On Critical Current For Spin Precession In Magnetic Multilayers

In magnetic multilayers, a dc current induces a spin precession above a certain critical current. Drive torques responsible for this can be calculated from the spin accumulation $\bar{\Delta\mu}$. Existing calculations of $\bar{\Delta\mu}$ assume a uniform cross section of conductors. But most multilayer samples are pillars with current leads flaring out immediately to a much wider cross-section area than that of the pillar itself. We write spin-diffusion equations of a form valid for variable cross section, and solve the case of flat electrodes with radial current distribution perpendicular to the axis of the pillar. Because of the increased volume available for conduction-electron spin relaxation in such leads, $\bar{\Delta\mu}$ is reduced in the pillar by at least a factor of 2 below its value for uniform cross section, for given current density in the pillar. Also, $\bar{\Delta\mu}$ and the critical current density for spin precession become nearly independent of the thickness of the pinned magnetic layer, and more dependent on the thickness of the spacer, in better agreement with measurements by Albert et al. (2002).Comment: To appear in J. Magn. Magn. Mate

Albert Fert

Albert Fert va néixer a Carcassona l'any 1938. Membre de l'Acadèmia Francesa de les Ciències, és professor de Física a la Universitat de París Sud des de l'any 1975. Entre els anys 1970 i 1975 va ser director de recerca al Laboratoire de Physique des Solides (Université Paris-Surd, Orsay) i, des del 1995 és director científic de la Unité Mixte de Physique CNRS/Thales (Palaiseau). L'activitat científica d'Albert Fert s'ha centrat en treballs experimentals i teòrics en el camp de la Física de la Matèria Condensada (metalls i aliatges, magnetisme, vidres d'espí, transport electrònic, nanostructures magnètiques i electrònica d'espí). Ha fet contribucions pioneres, fonamentalment relacionades amb el transport de càrrega depenent de l'espí que, finalment, el van portar a descobrir la GMR i a fer de l'espintrònica un nou camp de la ciència que pot rellevar l'electrònica actual. Fert va descobrir la GMR al mateix temps, encara que de manera independent, que el científic Peter Grunberg. Tots dos van rebre el Premi Nobel de Física 2007 per aquesta troballa, que es pot considerar la primera aplicació a gran escala de les noves nanotecnologies. Aquest efecte és la base de l'espintrònica, que explota la càrrega de l'electró i l'orientació de l'espí, o imant, per obtenir dispositius més petits i eficaços, i permet que puguin tenir noves funcionalitats. L'investigador francès ha publicat prop de 300 articles i ha col·laborat en 7 llibres. S'han fet més d'11.000 citacions dels seus articles. A més del Premi Nobel, ha rebut diversos guardons nacionals i internacionals, entre les quals cal remarcar el premi internacional James C. McGroddy Prize for New Materials de la Societat Americana de Física i el premi Europhysics de la Societat Europea de Física. Albert Fert col·labora estretament amb diferents centres de recerca i laboratoris del campus de la UAB, especialment amb l'ICMAB, que forma part del Parc de Recerca UAB. Ha estat vinculat també amb altres institucions científiques i universitàries catalanes, destacant la seva col·laboració activa en la creació de l'Institut Català de Nanotecnologia, centre del Parc de Recerca UAB, pel que fa a les línies de recerca que s'hi desenvolupenNomenament 21/05/2009. A proposta de Facultat de Ciències. Investidura 21/05/2009. Padrí: Josep Fontcubert