Josephson effect in SIFS-tunnel junctions with domain walls in weak link region

TL;DR

This paper provides a theoretical analysis of Josephson junctions with ferromagnetic domains, revealing how domain wall parameters influence critical current oscillations and proposing a new mechanism for observed experimental differences.

Contribution

The study introduces an analytical model for SIFS Josephson junctions with periodic magnetic domains, explaining the ratio of decay length to oscillation period as a function of domain parameters.

Findings

Critical current exhibits damped oscillations dependent on domain wall parameters.

The decay length and oscillation period ratio can vary from zero to one.

A new physical mechanism explains differences in decay and oscillation lengths in experiments.

Abstract

We study theoretically the properties of SIFS type Josephson junctions composed of two superconducting (S) electrodes separated by an insulating layer (I) and a ferromagnetic (F) film consisting of periodic magnetic domains structure with antiparallel magnetization directions in neighboring domains. The two-dimensional problem in the weak link area is solved analytically in the framework of the linearized quasiclassical Usadel equations. Based on this solution, the spatial distributions of the critical current density, $J_{C},$ in the domains and critical current, $I_{C},$ of SIFS structures are calculated as a function of domain wall parameters, as well as the thickness, $d_{F},$ and the width, $W,$ of the domains. We demonstrate that $I_{C}(d_{F},W)$ dependencies exhibit damped oscillations with the ratio of the decay length, $\xi_{1},$ and oscillation period, $\xi_{2},$ being a function of the parameters of the domains, and this ratio may take any value from zero to unity. Thus, we propose a new physical mechanism that may explain the essential difference between $\xi_{1}$ and $\xi_{2}$ observed experimentally in various types of SFS Josephson junctions.