Spintronics: Chiral damping

Abstract

The analysis of the magnetic domain wall motion in a nanostructured magnetic system with strong spin-orbit coupling shows that the energy dissipation can be chiral when the inversion symmetry is broken.

Figure 1. Handness and domain wall formation

a, Two spin structures with opposite handedness. Top and bottom configurations amount to left-handed and right-handed whirls, respectively, when the thumb of a left/right hand is pointed into the page and the other four fingers follow the red arrows. b, Domains and domain walls form in the trilayer Pt/Co/Pt. When an in-plane magnetic field H_ip is applied along +x direction, the magnetization at the center the domain walls is saturated along the +x direction. Then, the ↑↓ and ↓↑ domain walls acquire right- and left-handed cycloidal configurations, respectively. A driving field along -z direction pushes the two domain walls in opposite directions in order to expand ↓ domains

Figure 2. Domain wall speed v for the two domain walls with the opposite handedness

For both domain walls, log v as a function of H_z^−1/4 forms straight lines, yet the dependence is different depending on the handedness.