Enhancement of vortex pinning in superconductor/ferromagnet bilayers via angled demagnetization

TL;DR

This study demonstrates that magnetic domain width in superconductor/ferromagnet bilayers can be tuned via angled demagnetization to significantly enhance vortex pinning, especially when domain width matches the magnetic penetration depth.

Contribution

It introduces a method to control magnetic domain width in bilayers, leading to tunable vortex pinning enhancement in superconducting films.

Findings

Vortex pinning is maximized when domain width w is about 310 nm.

Pinning enhancement exceeds a factor of 10.

Adjusting domain width via demagnetization controls vortex behavior.

Abstract

We use local and global magnetometry measurements to study the influence of magnetic domain width w on the domain-induced vortex pinning in superconducting/ferromagnetic bilayers, built of a Nb film and a ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy, with an insulating layer to eliminate proximity effect. The quasi-periodic domain patterns with different and systematically adjustable width w, as acquired by a special demagnetization procedure, exert tunable vortex pinning on a superconducting layer. The largest enhancement of vortex pinning, by a factor of more than 10, occurs when w ~ 310 nm is close to the magnetic penetration depth.