YRLG Workshop: Correlation and Topology in magnetic materials, July 16th - 18th 2024
Mouad Fattouhi
Mouad Fattouhi∗,1, André Thiaville2, Felipe García-Sánchez1, Eduardo Martínez1, and Luis
López-Díaz1
1Departamento de Física Aplicada, Universidad de Salamanca, 37008, Salamanca, Spain
2Laboratoire de Physique des Solides, Université Paris-Saclay, CNRS, Orsay 91405, France
∗mfa@usal.es
Non-equilibrium dissipative systems in physical science have been widely studied in different areas, such as optics, fluids, and magnetism. Showing several interesting properties like pattern formation, self-organization phenomena, and spatiotemporal chaos, they were considered an appealing platform for many modern technologies [1]. In this work, we focus on investigating the spin-orbit torques (SOTs) induced dynamics of achiral domain walls (DWs) in perpendicularly magnetized strips using both analytical modeling and micromagnetic simulations. We show that depending on the strip width, such DWs depict distinct behaviors. For narrow strips, such DWs move with a velocity that
depends linearly on the applied current up to a threshold value, where it starts gradually decreasing and subsequently vanishes. For wide strips, however, we show that these DWs depict a variety of intricate states. First, around a threshold current, the DW completely stops moving similarly to the narrow strip case, but its internal magnetization develops a spatial pattern with complex transient dynamics. Using analytical modeling, we characterize the formed pattern as a 180◦-kink (180 degrees spin swirl) with ripple-like distortions of the DW shape, and we identify the key factors contributing to the formation of these kinks during the transient dynamics. Second, we demonstrate that if we continuously increase the current above the threshold, the system suffers multiple bifurcations, leading to an increase in the number of the formed kinks inside the DW. Last, at relatively high current values, we found that the DW exhibits spatiotemporal instabilities where, after a laminar phase, it changes
continuously its structure and shape in time or repeatedly cracks and recovers in a periodic manner. We relate all these observed states to soliton solutions found in different classes of physical systems described by the complex Ginzburg-Landau, reaction-diffusion, and Swift-Hohenberg equations [2, 3].
[1] M. Cross and H. Greenside, Pattern formation and dynamics in nonequilibrium systems (Cambridge University
Press, 2009).
[2] N. Akhmediev and A. Ankiewicz, Dissipative solitons in the complex ginzburg-landau and swift-hohenberg
equations, in Dissipative Solitons (Springer Berlin Heidelberg, Berlin, Heidelberg, 2005) pp. 1–17.
[3] H.-G. Purwins, H. Bödeker, and A. Liehr, Dissipative solitons in reaction-diffusion systems, Dissipative
Solitons (Springer Berlin Heidelberg, Berlin, Heidelberg, 2005) pp. 267–308.