Effect of spin transfer torque on domain wall motion regimes in [Co/Ni] superlattice wires

Abstract : In previous studies, we have shown that epitaxial Co/Ni(111) multilayers hold perpendicular magnetic anisotropy, low damping (down to 0.01) and high spin-polarization (up to 80%) at the Fermi level. Moreover, using Kerr microscopy, we have recently shown only few nucleation site per mm2 in our film. All these features place Co/Ni multilayer as model system to study phenomenon of DW motion induced by spin transfer torque (STT). Few groups around the world have reported results on STT-induced DW motion in Co/Ni wire. It is still unclear which of the adiabatic or non-adiabatic STT process is leading the DW motion in symmetric seed/[Co/Ni]x/cap stack. Here, we seek to answer to this question with well-controlled epitaxial [Co/Ni] grown by molecular beam epitaxy. We present a study on the combine effect of applied field and injected current on DW motion in a micro-wire using Kerr microscopy experiment. We demonstrate that the current has a strong impact on the two velocity regimes: thermally activated and precessional flow. The evolution of the DW velocity under combined pulsed field and current excitation is understood by taking into account both adiabatic and non-adiabatic components of STT. The parameters necessary to describe this behavior are extracted considering an Arrhenius law with an STT dependence. The measured DW velocities in the flow precessional regime are consistent with 1 dimensional model for DW motion using the previous extracted parameter. Finally, for large current density opposing the magnetic field, the DW motion direction is observed to be stochastic. Interestingly, we found that the DW can move in the electron flow direction against the external magnetic field, even for field amplitude as high as 20 mT. This effect has already been observed for Co/Ni device but no stochasticity was reported or predicted.
Type de document :
Poster
17ème Colloque Louis Néel, Mar 2016, Saint-Dié-des-Vosges, France
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https://hal-centralesupelec.archives-ouvertes.fr/hal-01579635
Contributeur : Sylvain Le Gall <>
Soumis le : jeudi 31 août 2017 - 14:24:17
Dernière modification le : mardi 21 août 2018 - 09:46:03

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  • HAL Id : hal-01579635, version 1

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Sylvain Le Gall, Nicolas Vernier, François Montaigne, André Thiaville, Dafiné Ravelosona, et al.. Effect of spin transfer torque on domain wall motion regimes in [Co/Ni] superlattice wires. 17ème Colloque Louis Néel, Mar 2016, Saint-Dié-des-Vosges, France. 〈hal-01579635〉

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