Current induced domain wall motion with a Ta/Gd-Fe/Si-N magnetic nanowire for a magneto-optical light modulator

Abstract

We investigated a magnetic nanowire device for a light modulator which is very important for 3D holography display application. It has a Si-N/Ta/Gd-Fe/Si-N nanowire with 0.5 × 17 μm2 dimension and a Co/Pd multilayer hard magnet with its size of 0.5 × 3 μm2 which is attached underneath the nanowire for initial domain nucleation. Both the nanowire and the hard magnet have perpendicular anisotropy. An initial domain was successfully nucleated by pulse current and found spin-orbit torque from Ta and local magnetic field from the nanomagnet was responsible for the domain nucleation. Current induced domain wall (DW) motion was observed and the DW moved along current direction without magnetic field. DW velocity was significantly enhanced with in-plane magnetic field (Hinp) of 25mT and velocity more than 200 m/s was obtained, which was more than 25 times faster than that without magnetic field. We also show that the fast DW velocity is attributed to chiral Neel domain wall induced by external in-plane magnetic field. This fast DW motion is very useful for large scale light modulator which refreshes large number of pixels, such as 10K × 10K pixels, over a limited time scale of 8 ∼ 16.7 ms which corresponds to TV frame rate of 120 or 60 Hz.