Very low critical current density for motion of coupled domain walls in synthetic ferrimagnet nanowires

Abstract

Domain walls in ferromagnetic nanowires are potential building-blocks of future technologies such as racetrack memories, in which data encoded in the domain walls are transported using spin-polarised currents. However, the development of energy-efficient devices has been hampered by the high current densities needed to initiate domain wall motion. We show here that a remarkable reduction in the critical current density can be achieved for in-plane magnetised coupled domain walls in CoFe/Ru/CoFe synthetic ferrimagnet tracks. The antiferromagnetic exchange coupling between the layers leads to simple Néel wall structures, imaged using photoemission electron and Lorentz transmission electron microscopy, with a width of only $\sim 100$~nm. The measured critical current density to set these walls in motion, detected using magnetotransport measurements, is $1.0\times 10^{11}$~Am${}^{-2}$, almost an order of magnitude lower than in a ferromagnetically coupled control sample. Theoretical modelling indicates that this is due to nonadiabatic driving of anisotropically coupled walls, a mechanism that can be used to design efficient domain-wall devices.

arXiv commentSupplmentary Information as ancillary file

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• L10 Fe-Pd Synthetic Antiferromagnet through an fcc Ru Spacer Utilized for Perpendicular Magnetic Tunnel Junctions
• Domain wall motion at low current density in a synthetic antiferromagnet nanowire
• Current distribution in metallic multilayers from resistance measurements
• Asymmetric depinning of chiral domain walls in ferromagnetic trilayers
• Diffusive and Fluid-like Motion of Homochiral Domain Walls in Easy-Plane Magnetic Strips
• Heat-Assisted Multiferroic Solid-State Memory
• Switching of biaxial synthetic antiferromagnets: a micromagentic study