Paramagnetic Meissner effect depending on superconducting thickness in Co/Nb multilayers

TL;DR

This study investigates how the paramagnetic Meissner effect in Co/Nb multilayers depends on the superconducting layer thickness, revealing a critical thickness related to the penetration depth necessary for PME occurrence.

Contribution

It demonstrates the dependence of PME on Nb layer thickness and links this to the penetration depth using a classical flux compression model.

Findings

PME observed only when Nb thickness exceeds penetration depth

Penetration depth is a critical length for PME occurrence

Flux compression model explains the data

Abstract

Paramagnetic Meissner Effect (PME) was observed in Co/Nb/Co trilayers and multilayers. Measurements of the response to perpendicular external field near the superconducting transition temperature were carried out for various Nb thicknesses. PME was found only when layer thickness is no smaller than penetration depth of Nb. A classical flux compression model [Koshelev and Larkin, Phys. Rev. B 52, 13559 (1995)] was used to explain our data. We inferred that the penetration depth was a critical length, below which superconducting current density became too small and the PME could not be achieved.