Vertical-current-induced domain-wall motion in MgO-based magnetic tunnel junctions with low current densities

Abstract

Shifting electrically a magnetic domain wall (DW) by the spin transfer mechanism 1-4 is one of the ways foreseen for the switching of future spintronic memories or registers 5,6 . But the classical geometries where the current is injected in the plane of the magnetic layers suffer from poor efficiencies of the intrinsic torques 7,8 acting on the DWs. A way to circumvent this problem is to use vertical-current injection 9-11 . For that case, theoretical calculations 12 attribute the microscopic origin of DW displacements to the out-of-plane ('field-like') spin-transfer torque 13,14 . Here we report experiments in which we controllably displace a DW in the planar electrode of a magnetic tunnel junction by vertical-current injection. Our measurements confirm the major role of the out-of-plane spin torque for DW motion, and allow quantifying this term precisely. The involved current densities are about 100 times smaller than the one commonly observed with in-plane currents 15 . Step-by-step resistance switching of the magnetic tunnel junction should provide a new approach to spintronic memristive devices 16-18 . © 2011 Macmillan Publishers Limited. All rights reserved.