Non-magnetic control of domain-walls in ferromagnetic nano-wires with perpendicular magnetic anisotropy

摘要

Materials with perpendicular magnetic anisotropy (PMA) provide an excellent platform for a novel class of memory and logic devices, e.g. exploiting transport and control of domain walls in ferromagnetic nanowires. In this paper we review some of our recent progress in this field, addressing control of domain wall motion by `non-magnetic' means, i.e. not exploiting magnetic fields or spin-injection from a ferromagnetic reservoir. First, we discuss experiments on electric field controlled domain wall motion. It is demonstrated that applying a voltage of just a few Volt across an insulating AlOx barrier on top of a Co/Pt thin film, domain wall velocities can be increased or decreased by up to an order of magnitude. Second, we discuss spin-orbit torques generated by the spin Hall effect as an effective way of current-induced domain wall motion. It is shown that the net effect can be accurately tuned in experiments on Pt/Co/Pt nanowires, and is governed by the internal structure of the domain wall. Finally, we propose a new approach in which the energy landscape experienced by the domain walls is engineered by focused ion-beam irradiation to favor unidirectional ratchet-like propagation. Importance of these findings for future application is discussed.