Fraunhofer patterns in magnetic Josephson junctions with non-uniform magnetic susceptibility

TL;DR

This paper models complex Fraunhofer patterns in magnetic Josephson junctions with non-uniform magnetic susceptibility, revealing how inhomogeneous magnetism affects critical current interference.

Contribution

It introduces a model for Fraunhofer patterns considering position- and field-dependent magnetic susceptibility in Josephson junction barriers, highlighting novel interference effects.

Findings

Predicted nonzero local minima in critical current

Identified non-periodic Fraunhofer patterns due to inhomogeneous magnetism

Showed interference effects between magnetised and demagnetised regions

Abstract

The development of superconducting memory and logic based on magnetic Josephson junctions relies on an understanding of junction properties and, in particular, the dependence of critical current on external magnetic flux (i.e. Fraunhofer patterns). With the rapid development of Josephson junctions with various forms of inhomogeneous barrier magnetism, Fraunhofer patterns are increasingly complex. In this paper we model Fraunhofer patterns for magnetic Josephson junctions in which the barrier magnetic susceptibility is position- and external magnetic field dependent. The model predicts anomalous Fraunhofer patterns in which local minima in the Josephson critical current can be nonzero and non-periodic with external magnetic flux due to an interference effect between highly magnetised and demagnetised regions.