Effect of ferromagnetic film thickness on magnetoresistance of thin-film superconductor-ferromagnet hybrids

TL;DR

This study investigates how the thickness of ferromagnetic films influences the superconducting properties of superconductor-ferromagnet hybrids, revealing optimal conditions for observing localized superconductivity and potential device applications.

Contribution

It demonstrates the impact of ferromagnetic film thickness on superconducting behavior, identifying an optimal thickness for broad non-monotonous Tc(H) dependence in S/F hybrids.

Findings

Increased ferromagnetic thickness broadens the Tc(H) dependence range.

Higher thickness leads to suppression of superconductivity.

Optimal thickness enables observation of localized superconductivity.

Abstract

We study the influence of the thickness Df of the plain ferromagnetic (F) film on the electrical resistance of the flux-coupled hybrids, consisting of superconducting (S) Al film and multilayer [Co/Pt] F film with out-of-plain magnetization. The behavior of such hybrids at high and low temperatures is found to be different: the nucleation of superconductivity at high temperatures is governed mainly by the typical lateral dimensions of the magnetic domains, while low temperature properties are determined by topology of the magnetic template. We show that an increase in the Df value leads to a broadening of the field- and temperature intervals where non-monotonous dependence of the superconducting critical temperature Tc on the applied magnetic field H is observed (for demagnetized F films). Further increase in the Df value results in a global suppression of superconductivity. Thus, we determined an optimal thickness, when the non-monotonous dependence Tc(H) can be observed in rather broad T and H range, what can be interesting for further studies of the localized superconductivity in planar Al-based S/F hybrids and for development of the devices which can exploit the localized superconductivity.