Current induced generation and synchronous motion of highly packed coupled chiral domain walls

摘要

Chiral domain walls of Neel type emerge in heterostructures that includeheavy metal (HM) and ferromagnetic metal (FM) layers owing to theDzyaloshinskii-Moriya (DM) interaction at the HM/FM interface. In developingstorage class memories based on the current induced motion of chiral domainwalls, it remains to be seen how dense such domain walls can be packedtogether. Here we show that a universal short range repulsion that scales withthe strength of the DM interaction exists among chiral domain walls. Thedistance between the two walls can be reduced with application of out of planefield, allowing formation of coupled domain walls. Surprisingly, the currentdriven velocity of such coupled walls is independent of the out of plane field,enabling manipulation of significantly compressed coupled domain walls usingcurrent pulses. Moreover, we find that a single current pulse with optimumamplitude can create a large number of closely spaced domain walls. Thesefeatures allow current induced generation and synchronous motion of highlypacked chiral domain walls, a key feature essential for developing domain wallbased storage devices.