First order phase transitions in Ferromagnet/Superconductor layered structures

TL;DR

This paper investigates first order phase transitions in layered ferromagnet/superconductor structures, revealing temperature-driven changes in junction configurations with measurable latent heats.

Contribution

It provides a self-consistent numerical analysis of phase transitions between different junction states in F/S layered structures, highlighting their first order nature.

Findings

Identification of first order phase transitions between 0 and π states.

Calculation of latent heats associated with these transitions.

Demonstration that these transitions are experimentally measurable.

Abstract

We study the thermodynamics of clean structures composed of superconductor (S) and ferromagnet (F) layers and consisting of one or more SFS junctions. We use fully self consistent numerical methods to compute the condensation free energies of the possible order parameter configurations as a function of temperature $T$. As $T$ varies, we find that there are phase transitions between states characterized by different junction configurations (denoted as ``0'' or ``$\pi$'' according to the phase difference of the order parameter in consecutive S layers). We show that these transitions are of first order. We calculate the associated latent heats and find them to be measurable.