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Domain walls in perpendicularly magnetized stripes violating spin-transfert torque ?

R. Lavrijsen


R. Lavrijsen(1), E. vd Bijl(2), R.A. Duine(2), J.T. Kohlhepp(1), H.J.M. Swagten(1), B. Koopmans(1)

(1) Department of applied physics, Eindhoven University of Technology, The Netherlands
(2) Institute for Theoretical Physics, Utrecht University, The Netherlands

 

The observation that current induced magnetic domain wall (DW) motion in perpendicularly magnetized Pt/Co/AlOx moves the DWs in the opposite direction as the electrons [1], violating the current theories on the subject, and the very recent discovery of a large Rashba spin-orbit field effect in this same material [2] has lead to a renewed interest for applications and scientific understanding of the underlying mechanisms. The high perpendicular magnetic anisotropy (PMA) in these systems lead to very narrow DWs predicted to enhance the interaction of a spin-polarized current with the local magnetization of the DW [3].

In this presentation we will show that a similar effect is observed in conventional Pt/Co/Pt and Pt/Co100-xBx/Pt layers [4,5]. We will speculate on the origin of the effect by varying the layers in the stack i.e. thickness, composition, and compare the results with calculations of the (spin-polarized) current distribution in the stack. Using a simple 1D DW model we show that the observed results can be explained by the in-plane Rashba field indicating that it can be tuned by simply varying the layer thicknesses.

 

[1] T.A. Moore et al., Appl. Phys. Lett 93, 262504, (2008) & 95, 179902, (2009)
[2] I.M. Miron et al., Nature Mat. 2613 (2010)
[3] C. Burrowes et al., Nature Phys. 1436 (2009)
[4] R. Lavrijsen, et al., Appl. Phys. Lett. 96, 022501, (2010)
[5] L. San Emeterio Alvarez, et al., Phys. Rev. Lett. 104, 137205 (2010)