Piezoelectric and photon helicity dependent domain wall motion driven by electrical current and optical spin transfer torques

Summary form only given. The rich internal degrees of freedom of magnetic domain walls (DW) make them an attractive complement to electron charge for exploring new concepts of storage, transport, and processing of information. We utilize the tuneable internal structure of a DW in perpendicularly magnetized GaMnAsP/GaAs ferromagnetic semiconductor and demonstrate devices in which piezo-electrically controlled magnetic anisotropy yields large mobility variations for current driven DW motion . [1, 2] We directly observe and piezo-electric control the Walker breakdown separating two regimes with different mobilities . The piezo-electric control allows to experimentally assess the upper and lower boundaries of the characteristic ratio of adiabatic and non-adiabatic spin transfer torques in the current driven DW motion . Apart from current induced DW motion, also optically generated electron spins can move DWs . The direction of DW motion depends on the photon helicity in our GaMnAsP/GaAs devices and we identify optical spin transfer torque (oSTT) [4] as the underlying mechanism . We further discuss possibilities to apply and electrically control oSTT induced DW motion to thin magnetic metal films . Optically driven DW motion can be very efficient and high velocities maybe achieved since intrinsic DW pinning [5] does not occur when the entire DW is simultaneously exposed to perpendicular polarized electron spins . We also identify a polarisation independent contribution for light-induced DW motion where the DW is attracted to the hot-spot generated by the focused laser light . Unlike magnetic field and current driven DW motion, light-induced DW motion provides an optical tweezers like ability to position and locally probe DWs .