Coexistence of superconductivity and complex 4$f$ magnetism in Eu$_{0.5}$Ce$_{0.5}$BiS$_{2}$F

TL;DR

This study reports the coexistence of superconductivity and complex 4f magnetism in Eu0.5Ce0.5BiS2F, revealing distinct magnetic and superconducting phases and their potential interactions.

Contribution

It demonstrates the coexistence of ferromagnetism and superconductivity in a Eu-Ce substituted BiS2F compound, with insights into their possible microscopic mechanisms.

Findings

Superconductivity at 2.2 K in Eu0.5Ce0.5BiS2F

Ferromagnetic order at 8 K for Ce-4f moments

Possible antiferromagnetic order at 2.1 K for Eu-4f spins

Abstract

EuBiS$_{2}$F is a self-doped superconductor due to the mixed valence of Eu. Here we report that, with the Ce substitution for Eu by 50 at.\%, the material exhibits ferromagnetic ordering at 8 K for the Ce-4$f$ moment, superconductivity at 2.2 K in the BiS$_2$ layers, and possibly antiferromagnetic ordering at 2.1 K for the Eu-4$f$ spins. The Eu valence is essentially divalent with the Ce incorporation. We tentatively interpret the coexistence of ferromagnetism and superconductivity by considering different Bi-6$p$ orbitals that are responsible for superconductivity itself and for mediating the ferromagnetic interaction, respectively. We argue that the antiferromagnetic ordering of the Eu-4$f$ spins is most likely due to a magnetic dipole-dipole interaction.