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46 results on '"Valet, T."'

1. Extrinsic spin Hall effects measured with lateral spin valve structures

Author

Niimi, Y., Suzuki, H., Kawanishi, Y., Omori, Y., Valet, T., Fert, A., and Otani, Y.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

The spin Hall effect (SHE), induced by spin-orbit interaction in nonmagnetic materials, is one of the promising phenomena for conversion between charge and spin currents in spintronic devices. The spin Hall (SH) angle is the characteristic parameter of this conversion. We have performed experiments of the conversion from spin into charge currents by the SHE in lateral spin valve structures. We present experimental results on the extrinsic SHEs induced by doping nonmagnetic metals, Cu or Ag, with impurities having a large spin-orbit coupling, Bi or Pb, as well as results on the intrinsic SHE of Au. The SH angle induced by Bi in Cu or Ag is negative and particularly large for Bi in Cu, 10 times larger than the intrinsic SH angle in Au. We also observed a large SH angle for CuPb but the SHE signal disappeared in a few days. Such an aging effect could be related to a fast mobility of Pb in Cu and has not been observed in CuBi alloys., Comment: 12 pages, 10 figures

Published
2014
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2. Giant Spin Hall Effect Induced by Skew Scattering from Bismuth Impurities inside Thin Film CuBi Alloys

Author

Niimi, Y., Kawanishi, Y., Wei, D. H., Deranlot, C., Yang, H. X., Chshiev, M., Valet, T., Fert, A., and Otani, Y.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

We demonstrate that a giant spin Hall effect (SHE) can be induced by introducing a small amount of Bi impurities in Cu. Our analysis based on a new 3-dimensional finite element treatment of spin transport shows that the sign of the SHE induced by the Bi impurities is negative and its spin Hall (SH) angle amounts to -0.24. Such a negative large SH angle in CuBi alloys can be explained by applying the resonant scattering model proposed by Fert and Levy [Phys. Rev. Lett. 106, 157208 (2011)] to 6p impurities., Comment: 5 pages, 4 figures

Published
2012
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6. High track density magneto-optical readout of magnetic tapes

Author

Maillot, C., Blanchard, N., Valet, T., and Lehureau, J.C.

Subjects
Magneto-optics -- Research, Magnetic tapes -- Research, Storage density -- Research, Business, Electronics, Electronics and electrical industries
Abstract

The track resolution capability of a new magneto-optical multitrack readout head for magnetic tape is evaluated. The magnetic contribution to the track to track crosstalk is experimentally measured through the optical scanning of the transducer. This experimental measurement is compared to 3D transmission line calculation and to finite element simulation. Anisotropy of soft poles leads to a strong decrease of magnetic crosstalk. The optical contribution to the crosstalk is also calculated. These results permit one to foresee that this magneto-optical thin film technology will be able to accomodate very high track density up to the optical resolution limit (2.5 ktpi) despite the continuous structure of the poles.

Published
1994

10. Coercivity and magnetization process versus dipolar coupling in Ni80Fe20/Cu/Co/Cu spin valves

Author

Kergoat, R., Miltat, J., Valet, T., and Jerome, R.

Subjects
Thin films, Multilayered -- Research, Magnetization -- Analysis, Physics
Abstract

Magnetization studies of Ni80Fe20/Cu/Co exchange coupled multilayers show the presence of magnetic fluctuations. The distribution in the soft layer causes magnetic fluctuations. Kerr microscopic studies reveal the effect of dipolar coupling on the layer properties of the alloy, with an increase in the coercive field of the NiFe film.

Published
1994

11. Correlation between magnetic and structural properties of Ni80Fe20 sputtered thin films deposited on Cr and Ta buffer layers

Author

Jerome, R., Valet, T., and Galtier, P.

Subjects
Thin films -- Magnetic properties, Thin films, Multilayered -- Research, Sputtering (Physics) -- Research, Business, Electronics, Electronics and electrical industries
Abstract

We studied the magnetic properties and structure of sputtered [Ni.sub.80][Fe.sub.20] films, on Si(100) substrates with either a Cr or Ta buffer. The films deposited on Ta buffers exhibit a very low coercive field (Hc [is approximately equal to] 0.9 Oe), much smaller than those deposited on Cr buffers (Hc [is approximately equal to] 2.5 Oe). Moreover, by transmission electron microscopy (both plane views and cross-sections), it was established that the Ta buffer induces a marked (111) perpendicular texture and a small lateral grain size (D [is approximately equal to] 150 [Angstrom]). This is in strong contrast with the absence of any preferential orientation and the larger crystalite size (D [is approximately equal to] 400 [Angstrom]) of the firms deposited on Cr. The very low coercivity obtained on Ta buffers is tentatively explained considering that the film geometry, together with the induced texture, constrained the magnetization to lie in (111) crystallographic planes, which is shown to strongly suppress the possible sources of local anisotropy fluctuations.

Published
1994

12. Initial rotational susceptibility of exchange coupled permalloy/copper/cobaltmultilayers

Author

Kergoat, R., Labrune, M., Miltat, J., Valet,T., and Jacquet, J.C.

Subjects
Magnetic materials -- Research, Ferromagnetism -- Research, Business, Electronics, Electronics and electrical industries
Abstract

Exchange coupled Permalloy/Copper/Cobalt multilayers are observed by Kerr microscopy. The stability of 180 degrees walls is investigated by applying fields transverse to the initial saturation field. The experiments show that the anisotropy is not as small as previously assumed, but is determined by the initial field. In contrast to the samples with ferromagnetic coupling, the preexisting walls in antiferromagnetically coupled samples can easily be annihilated using transverse fields. This can be explained by particular combinations of coupling strength and anisotropy.

Published
1993

13. Magnetoresistance in rf-sputtered (NiFe/Cu/Co/Cu) spin-valve multilayers

Author

Lottis, D., Fert, A., Morel, R., Pereira, L.G., Jacquet, J.C., Galtier, P., Coutellier, J.M., and Valet, T.

Subjects
Thin films, Multilayered -- Research, Antiferromagnetism -- Research, Thin films -- Magnetic properties, Physics
Abstract

Variations in the magnetoresistance (MR) of NiFe/Cu/Co/Cu spin-valve multilayered structures with thicknesses tNiFe, tCo and tCu were investigated. The results showed that in the case of tCu, there was an oscillatory interlayer exchange coupling through the Cu layers with a period of around 12 angstroms. However, coupling in tNiFe and tCo was negligible and MR was dominated by the thickness dependence of the NiFe and Co component layer coercivities.

Published
1993

17. Identification and selection rules of the spin-wave eigenmodes in a normally magnetized nanopillar

Author

Naletov, V. V., primary, de Loubens, G., additional, Albuquerque, G., additional, Borlenghi, S., additional, Cros, V., additional, Faini, G., additional, Grollier, J., additional, Hurdequint, H., additional, Locatelli, N., additional, Pigeau, B., additional, Slavin, A. N., additional, Tiberkevich, V. S., additional, Ulysse, C., additional, Valet, T., additional, and Klein, O., additional

Published
2011
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34. Complete mapping of the spin-wave spectrum in a vortex-state nanodisk

Author

Taurel B., Valet T., Naletov V., Vukadinovic N., De Loubens G., Klein O., Taurel B., Valet T., Naletov V., Vukadinovic N., De Loubens G., and Klein O.

Abstract

© 2016 American Physical Society.We report a study on the complete spin-wave spectrum inside a vortex-state nanodisk. Transformation of this spectrum is continuously monitored as the nanodisk becomes gradually magnetized by a perpendicular magnetic field and encounters a second-order phase transition to the uniformly magnetized state. This reveals the bijective relationship that exists between the eigenmodes in the vortex state and the ones in the saturated state. It is found that the gyrotropic mode can be continuously viewed as a uniform phase precession, which uniquely softens (its frequency vanishes) at the saturation field to transform above into the Kittel mode. By contrast, the other spin-wave modes remain finite as a function of the applied field, while their character is altered by level anticrossing.

35. Complete mapping of the spin-wave spectrum in a vortex-state nanodisk

Author

Taurel B., Valet T., Naletov V., Vukadinovic N., De Loubens G., Klein O., Taurel B., Valet T., Naletov V., Vukadinovic N., De Loubens G., and Klein O.

Abstract

© 2016 American Physical Society.We report a study on the complete spin-wave spectrum inside a vortex-state nanodisk. Transformation of this spectrum is continuously monitored as the nanodisk becomes gradually magnetized by a perpendicular magnetic field and encounters a second-order phase transition to the uniformly magnetized state. This reveals the bijective relationship that exists between the eigenmodes in the vortex state and the ones in the saturated state. It is found that the gyrotropic mode can be continuously viewed as a uniform phase precession, which uniquely softens (its frequency vanishes) at the saturation field to transform above into the Kittel mode. By contrast, the other spin-wave modes remain finite as a function of the applied field, while their character is altered by level anticrossing.

36. Identification and selection rules of the spin-wave eigenmodes in a normally magnetized nanopillar

Author

Naletov V., De Loubens G., Albuquerque G., Borlenghi S., Cros V., Faini G., Grollier J., Hurdequint H., Locatelli N., Pigeau B., Slavin A., Tiberkevich V., Ulysse C., Valet T., Klein O., Naletov V., De Loubens G., Albuquerque G., Borlenghi S., Cros V., Faini G., Grollier J., Hurdequint H., Locatelli N., Pigeau B., Slavin A., Tiberkevich V., Ulysse C., Valet T., and Klein O.

Abstract

We report on a spectroscopic study of the spin-wave eigenmodes inside an individual normally magnetized two-layer circular nanopillar (permalloy|copper|permalloy) by means of a magnetic resonance force microscope. We demonstrate that the observed spin-wave spectrum critically depends on the method of excitation. While the spatially uniform radio-frequency (rf) magnetic field excites only the axially symmetric modes having azimuthal index =0, the rf current flowing through the nanopillar, creating a circular rf Oersted field, excites only the modes having azimuthal index =+1. Breaking the axial symmetry of the nanopillar, either by tilting the bias magnetic field or by making the pillar shape elliptical, mixes different index symmetries, which can be excited simultaneously by the rf current. Experimental spectra are compared to theoretical prediction using both analytical and numerical calculations. An analysis of the influence of the static and dynamic dipolar coupling between the nanopillar magnetic layers on the mode spectrum is performed. © 2011 American Physical Society.

37. Complete mapping of the spin-wave spectrum in a vortex-state nanodisk

Author

Taurel B., Valet T., Naletov V., Vukadinovic N., De Loubens G., Klein O., Taurel B., Valet T., Naletov V., Vukadinovic N., De Loubens G., and Klein O.

Abstract

© 2016 American Physical Society.We report a study on the complete spin-wave spectrum inside a vortex-state nanodisk. Transformation of this spectrum is continuously monitored as the nanodisk becomes gradually magnetized by a perpendicular magnetic field and encounters a second-order phase transition to the uniformly magnetized state. This reveals the bijective relationship that exists between the eigenmodes in the vortex state and the ones in the saturated state. It is found that the gyrotropic mode can be continuously viewed as a uniform phase precession, which uniquely softens (its frequency vanishes) at the saturation field to transform above into the Kittel mode. By contrast, the other spin-wave modes remain finite as a function of the applied field, while their character is altered by level anticrossing.

38. Complete mapping of the spin-wave spectrum in a vortex-state nanodisk

Author

Taurel B., Valet T., Naletov V., Vukadinovic N., De Loubens G., Klein O., Taurel B., Valet T., Naletov V., Vukadinovic N., De Loubens G., and Klein O.

Abstract

© 2016 American Physical Society.We report a study on the complete spin-wave spectrum inside a vortex-state nanodisk. Transformation of this spectrum is continuously monitored as the nanodisk becomes gradually magnetized by a perpendicular magnetic field and encounters a second-order phase transition to the uniformly magnetized state. This reveals the bijective relationship that exists between the eigenmodes in the vortex state and the ones in the saturated state. It is found that the gyrotropic mode can be continuously viewed as a uniform phase precession, which uniquely softens (its frequency vanishes) at the saturation field to transform above into the Kittel mode. By contrast, the other spin-wave modes remain finite as a function of the applied field, while their character is altered by level anticrossing.

39. Identification and selection rules of the spin-wave eigenmodes in a normally magnetized nanopillar

Author

Naletov V., De Loubens G., Albuquerque G., Borlenghi S., Cros V., Faini G., Grollier J., Hurdequint H., Locatelli N., Pigeau B., Slavin A., Tiberkevich V., Ulysse C., Valet T., Klein O., Naletov V., De Loubens G., Albuquerque G., Borlenghi S., Cros V., Faini G., Grollier J., Hurdequint H., Locatelli N., Pigeau B., Slavin A., Tiberkevich V., Ulysse C., Valet T., and Klein O.

Abstract

We report on a spectroscopic study of the spin-wave eigenmodes inside an individual normally magnetized two-layer circular nanopillar (permalloy|copper|permalloy) by means of a magnetic resonance force microscope. We demonstrate that the observed spin-wave spectrum critically depends on the method of excitation. While the spatially uniform radio-frequency (rf) magnetic field excites only the axially symmetric modes having azimuthal index =0, the rf current flowing through the nanopillar, creating a circular rf Oersted field, excites only the modes having azimuthal index =+1. Breaking the axial symmetry of the nanopillar, either by tilting the bias magnetic field or by making the pillar shape elliptical, mixes different index symmetries, which can be excited simultaneously by the rf current. Experimental spectra are compared to theoretical prediction using both analytical and numerical calculations. An analysis of the influence of the static and dynamic dipolar coupling between the nanopillar magnetic layers on the mode spectrum is performed. © 2011 American Physical Society.

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