Current-based control of magnetization switching and chiral magnetic domain walls motion in ultra-thin films

Electrical magnetization manipulation in nanostructures is a central requirement for new magnetic memory, logic and sensor devices. This part of my work explores the possibility of controlling the magnetization switching process and the domain wall motion in magnetic thin films lacking structural inversion symmetry (SIS). The breaking of SIS in  obtained by sandwiching a thin magnetic layer between two different non-magnetic layers, like in the case of Ta\CoFeB\MgO and Pt\Co\AlOx. In those types of materials systems, the magnetic layer is grown on top of a heavy metal (Ta,Pt) and covered by an oxide layer (MgO, AlOx) so to break the inversion symmetry of the system. Due to the structural inversion asymmetry, chiral magnetic domain walls are stabilized in those systems, so that the magnetic moments in the domain walls always rotate in the same way (clockwise or counter-clockwise). Furthermore, due to the presence of the heavy metal at the bottom, an effective spin-injection in the magnetic layer is obtained when an electric current flows, in-plane, through the materials stack. As a result of that, a huge torque (named spin-orbit torque, SOT) can be applied of the magnetic layer, inducing the switching of the magnetization state in the magnetic layer. Furthermore, the same SOT can also induce a very fast domain wall motion.

Current-induced magnetization switching in  Ta\CoFeB\MgO nanowires by SOT. (a) Experimental setup. (b) Initial magnetization state pointing down (light grey). (c) Current-induced final magnetization state pointing up (dark grey). See publication in Appl. Phys. Lett.

Current-induced domain walls motion in  Ta\CoFeB\MgO nanowires by SOT. (a) Experimental setup. (b) Initial domain walls position. (c) Current-induced final domain walls position. See publication in Phys. Rev. B.