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As the data modern societies generate and consume increases exponentially, faster and more energy efficient data handling are sought. Innovations integrating photonic components with electronics are vastly improving the performance of data handling, while bottlenecks form where the conversion of electrical to optical signals (or vice-versa) take place. This work presents a hybrid photonic device which mediates direct optical communication with non-volatile magnetic memory and promises on-chip all-optical reading of magnetically stored information.

Magnetic thin films with Dzyaloshinskii-Moriya interactions (DMI) are receiving enormous interest because of recent developments in the understanding of DMI's role in controlling the efficiency of domain wall (DW) motion [1] and in creating magnetic skyrmions [2]. Recently, interfacial DMI has been proposed to be directly related to Rashba spin-orbit coupling at magnetic interfaces [3]. Based on this theory, magnetic domain-wall (DW) resistance is predicted to gain an additional term originating from the Rashba effect. We call this extra term 'chiral resistance', as the sign opposite for DWs with different chiralities, which means that electrons have different scattering rates when moving through DWs with positive and negative chiralities. Since this chiral resistance solely originates from Rashba effect, a direct observation can help to illuminate the debated roles of DMI and Rashba versus Spin-Hall effects for fast current-driven domain wall motion [4]. Moreover, this chiral resistance can be very useful for designing future energy-efficient domain wall devices, e.g. if we combine it with the recently proposed electric-field control of DW chirality [5].

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.