In situ transport characterization of magnetic states in Nb/Co superconductor/ferromagnet heterostructures

TL;DR

This study uses in situ transport measurements and advanced analysis techniques to detail the magnetic state transitions in Nb/Co superconductor/ferromagnet heterostructures, crucial for developing novel superconducting devices.

Contribution

It introduces the application of FORC analysis for detailed in situ magnetic state characterization in Nb/Co heterostructures, revealing complex magnetization behaviors.

Findings

Magnetization rotates coherently before switching abruptly.

Magnetic states evolve through polydomain configurations.

Transport measurements correlate with magnetic state transitions.

Abstract

Employment of the non-trivial proximity effect in superconductor/ferromagnet (S/F) heterostructures for the creation of novel superconducting devices requires accurate control of magnetic states in complex thin-film multilayers. In this work, we study experimentally in-plane transport properties of microstructured Nb/Co multilayers. We apply various transport characterization techniques, including magnetoresistance, Hall effect, and the first-order-reversal-curves (FORC) analysis. We demonstrate how FORC can be used for detailed in situ characterization of magnetic states. It reveals that upon reduction of the external field, the magnetization in ferromagnetic layers first rotates in a coherent scissor-like manner, then switches abruptly into the antiparallel state and after that splits into the polydomain state, which gradually turns into the opposite parallel state.