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Séminaire « Magnétisme et physique du spin »

Magnetic and transport characterization of nanostructured skyrmion based multilayers - Davide Maccariello - Mardi 27 septembre 2016 à 11 h

INSP - UPMC - 4 place Jussieu - 75005 Paris - Barre 22-32, 2e étage, salle 201

Davide Maccariello - Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay

Abstract

Magnetic skyrmions are non-trivial spin textures that can form in materials that break the inversion symmetry [1]. Crucial for the stabilization of skyrmions is the Dzyaloshinskii-Moriya interaction (DMI). In thin films, the DMI is due to the combination of strong spin-orbit interaction in an adjacent heavy metal non-magnetic layer and the broken symmetry at the interface of the magnetic material [2].

In this seminar, I will present the main results we have obtained on several multilayered systems in which the thin ferromagnetic layer is inserted between two heavy metals in the form of NM1|Co|NM2 (NM1,NM2 being Pt,Ir or AlOx) in order to have additive chiral interaction from both interfaces. The layer thicknesses and the number of the NM1|Co|NM2 repetitions have been varied in order to favor the formation and stabilization of individual sub-100 nm skyrmions under ambient conditions [4]. I have performed a comprehensive electrical transport characterization (both longitudinal magnetoresistance and transverse Hall voltage) obtained at room temperature on different nanostructured multilayers with perpendicular-to-plane magnetic anisotropy (PMA) (fig.1a). Using magnetic imaging by Magnetic Force Microscopy, I will show how it is possible to extract an estimation of the DMI magnitude [4] and to link the transport measurements with the actual magnetic configuration in the track devices. As shown in Figure 1, we prepare magnetically the system so as to stabilize a discrete number of skyrmions in confined nanostructures of different NM1|Co|NM2 multilayers (fig.1b-c). We will discuss the concomitant detection of clear signature in the magnetoresistance or Hall voltage, thus allowing an electrical detection of individual small skyrmions.

Room temperature observation of skyrmions [4] can be a robust basis of the development of skyrmion-based devices for memory and/or logic applications as well of the starting point of further fundamental studies on their very rich physics.

ANR ULTRASKY and EU grant MAGicSky No. FET-Open-665095 are acknowledged for financial support.

1. A.N. Bogdanov, U.K. Rossler Phys. Rev. Lett. 87, 037203 (2001).
2. A. Fert Mater. Sci. Forum 59–60, 439–480 (1990). A. Fert, P. M. Levy Phys. Rev. Lett. 44, 1538–1541 (1980).
3.K. von Bergmann, S. Heinze, M. Bode, E.Y. Vedmedenko, G. Bihlmayer, S. Blugel, and R. Wiesendanger Phys. Rev. Lett. 96, 167203 (2006).
4. C. Moreau Moreau-Luchaire et al Nature Nanotechnology 11, 444–448 (2016).
5. H. Nakayama et al. Phys. Rev. Lett. 110, 206601 (2013).