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

TL;DR

This paper demonstrates that vertical current injection in MgO-based magnetic tunnel junctions can efficiently move magnetic domain walls using low current densities, highlighting the role of out-of-plane spin transfer torque.

Contribution

It provides experimental evidence and quantification of out-of-plane spin transfer torque as the main driver for domain wall motion in vertical current configurations.

Findings

Domain walls can be displaced with current densities 100 times lower than in-plane methods.

Out-of-plane spin transfer torque is confirmed as the primary mechanism for DW motion.

Vertical current injection enables step-by-step resistance switching in magnetic tunnel junctions.

Abstract

Shifting electrically a magnetic domain wall (DW) by the spin transfer mechanism is one of the future ways foreseen for the switching of spintronic memories or registers. The classical geometries where the current is injected in the plane of the magnetic layers suffer from a poor efficiency of the intrinsic torques acting on the DWs. A way to circumvent this problem is to use vertical current injection. In that case, theoretical calculations attribute the microscopic origin of DW displacements to the out-of-plane (field-like) spin transfer torque. 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 to quantify this term precisely. The involved current densities are about 100 times smaller than the one commonly observed with in-plane currents. Step by step resistance switching of the magnetic tunnel junction opens a new way for the realization of spintronic memristive devices.