Magnetic proximity effects in V/Fe superconductor/ferromagnet single bilayer revealed by waveguide-enhanced polarized neutron reflectometry

TL;DR

This study uses waveguide-enhanced polarized neutron reflectometry to reveal a new magnetic state induced by the proximity effect in a single superconductor/ferromagnet bilayer, showing temperature-dependent magnetic behavior.

Contribution

It demonstrates the first use of waveguide resonance to study magnetic proximity effects in a single SC/FM bilayer, excluding multilayer artifacts.

Findings

A new magnetic state appears below 0.7 TC.

The magnetic state decays gradually as temperature approaches TC.

Diffuse scattering increases by 5% with temperature.

Abstract

Polarized neutron reflectometry is used to study the magnetic proximity effect in a superconductor/ferromagnet (SC/FM) system of composition Cu(32nm)/V(40nm)/Fe(1nm)/MgO. In contrast to previous studies, here a single SC/FM bilayer, is studied and multilayer artefacts are excluded. The necessary signal enhancement is achieved by waveguide resonance, i.e. preparing the V(40nm)/Fe(1nm) SC/FM bilayer sandwiched by the highly reflective MgO substrate and Cu top layer, respectively . A new magnetic state of the system was observed at temperatures below 0.7 TC. manifested in a systematic change in the height and width of the waveguide resonance peak. Upon increasing the temperature from 0.7 TC to TC, a gradual decay of this state is observed, accompanied by a 5% growth of the diffuse scattering. According to theoretical studies, such behavior is the result of the magnetic proximity effect. Due to the presence of the thin FM layer the superconducting electrons are polarized and, as a result, near the SC/FM interface an additional magnetic layer appears in the SC with thickness comparable to ksi, the coherence length of the superconductor.