June 6, 2012 Wednesday 10:00
Eduardo Martinez, Universidad de Salamanca
Current-driven domain wall propagation along strips with high perpendicular magnetocristalline anisotropy: A micromagnetic analysis of the Rashba field in asymmetric stacks

Abstract:Several logic [1] and memory [2] devices based on the motion of Domains Walls (DWs) have been proposed over the last years. Traditionally, DWs are driven by magnetic fields [1], but in recent years, new paradigms for DW-based devices have been made possible by injecting spin polarized currents through the mechanism of the spin-momentum transfer [2]. These new architectures involve a precise understanding of the DW motion along ferromagnetic strips, it is of crucial importance to determine how thermal fluctuations influence on the DW dynamics along strips with some degree of structural imperfection. The study is also of fundamental interest, because the comparison between realistic theoretical predictions and experimental observations could help to determine intrinsic quantities such as polarization factor and the magnitude of the non-adiabatic spin torque.

This talk will be focused on characterizing the DW dynamics along strips with high Perpendicular Magnetocristalline Anisotropy (PMA) from a theoretical point of view, by using both a full micromagnetic description and the one-dimensional model, including thermal effects and surface roughness. Experimental measurements of DW dynamics along high PMA strips indicate a low operation current with reduced unwanted Joule heating, and they have been performed in several architectures, ranging from single-layer [3] to multilayer stacks [4]. Particularly interesting are the experiments on DW propagation along a high PMA Cobalt strip sandwiched between two dissimilar non-magnetic layers (Pt/Co/AlO), which have pointed out a high spin-torque efficiency leading to very high DW velocities [4]. The suggested reason for this behavior is the Spin-Orbit Interaction (SOI) on the conduction electrons, which originates from the structural inversion asymmetry (SIA) of the multilayer stack, and it is mediated by an effective Rashba magnetic field. In the talk, a realistic micromagnetic study of the Rashba field will be presented with the aim of analyzing its effect on the current-driven DW propagation along high PMA strips sandwiched between two dissimilar non-magnetic layers with SOI [5]. The results will be also compared to the ones [6] obtained for a single layer strip where the SOI is negligible.

[1] D. A. Allwood et al, Science, 296, 2003 (2002).
[2] S. S. P. Parkin, U. S. Patent, 6834005 (2004).
[3] C. Burrowes et al. Nat. Phys. 6, 17 (2010).
[4] I. M. Miron et al. Nat. Mat. 10, 419 (2011).
[5] E. Martinez. Accepted in J. Appl. Phys.
[6] E. Martinez . To appear in J. Phys.: Condens. Matter. December (2011).

Bio: Eduardo Martinez was born in La BaƱeza, Leon ( Spain ) in 1975. He received a B. S. in Physics in 2001, and a Ph. D. in Mathematics and Physics in 2005, both from the University of Salamanca ( Spain ).
He jointed to the Department of Applied Physics of the University of Salamanca as a Research staff in 2003. In October 2005, Dr. Martinez moved to the University of Burgos ( Spain ) where he worked as Assistant Professor in the Department of Electromechanical Engineering. From October 2009, Dr. Martinez works as Assistant Professor in the Department of Applied Physics of the University of Salamanca . His main interest research is micromagnetic modelling and novel spintronic effects and devices. Over the course if his research, he has studied thermal effects, the influence of the eddy currents on the magnetization dynamics, spin-transfer torque and several issues related to domain wall motion along ferromagnetic strips.