Investigation of magnetic droplet solitons using x-ray holography with extended references

E. Burgos-Parra (1) , N. Bukin (1) , S. Sani , A. I Figueroa (2) , Guillaume Beutier (3) , M. Dupraz (3) , S. Chung (4, 5) , P. Dürrenfeld (4) , Q. Tuan Tuan Le (4, 5) , S. M Mohseni (6) , A. Houshang (4) , S. A Cavill (7) , R J Hicken (1) , J. Åkerman (4) , G. van Der Laan (2) , F. y Ogrin (1)

1 School of Physics and Astronomy [Exeter]
2 Magnetic Spectroscopy Group
3 SIMaP - Science et Ingénierie des Matériaux et Procédés
4 GU - Göteborgs Universitet = University of Gothenburg
5 Department of Physics and Astronomy [Uppsala]
6 Shahid Beheshti University
7 Department of Physics, University of York, Heslington, York YO10 5DD, United Kingdom

A dissipative magnetic soliton, or magnetic droplet, is a structure that has been predicted to exist within a thin magnetic layer when non-linearity is balanced by dispersion, and a driving force counteracts the inherent damping of the spin precession. Such a soliton can be formed beneath a nano-contact (NC) that delivers a large spin-polarized current density into a magnetic layer with perpendicular magnetic anisotropy. Although the existence of droplets has been confirmed from electrical measurements and by micromagnetic simulations, only a few attempts have been made to directly observe the magnetic landscape that sustains these structures, and then only for a restricted set of experimental parameter values. In this work we use and x-ray holography technique HERALDO, to image the magnetic structure of the [Co/Ni]x4 multilayer within a NC orthogonal pseudo spin-valve, for different range of magnetic fields and injected electric currents. The magnetic configuration imaged at-33 mA and 0.3 T for devices with 90nm NC diameter reveals a structure that is electrically and spatially consistent with a droplet soliton. We also report the magnetisation configurations observed at lower DC currents in the presence of fields (0-50 mT), where it is expected to observe regimes of the unstable droplet formation..

Domaines: Science des matériaux [cond-mat.mtrl-sci]; Electrons fortement corrélés [cond-mat.str-el]; Matériaux

E. Burgos-Parra, N. Bukin, S. Sani, A. I Figueroa, Guillaume Beutier, et al.. Investigation of magnetic droplet solitons using x-ray holography with extended references. Scientific Reports, 2018, 8 (11533), ⟨10.1038/s41598-018-29856-y⟩. ⟨hal-01900884⟩