Interplay of antiferromagnetism, ferromagnetism and superconductivity in EuFe_2(As_1-xP_x)_2 single crystals

TL;DR

This study explores how antiferromagnetic and ferromagnetic Eu^2+ magnetic phases influence superconductivity in EuFe_2(As_1-xP_x)_2 single crystals, revealing coexistence and competition between magnetism and superconductivity through experiments and calculations.

Contribution

It provides a detailed experimental and theoretical analysis of magnetic phases and their impact on superconductivity in EuFe_2(As_1-xP_x)_2, highlighting the coexistence and competition of these states.

Findings

Superconductivity appears at x=0.16 and 0.20 with T_c of 22 K and 28 K.

Eu ions switch from antiferromagnetic to ferromagnetic order as x increases.

Density functional theory calculations support experimental phase behavior.

Abstract

We report a systematic study on the influence of antiferromagnetic and ferromagnetic phases of Eu^2+ moments on the superconducting phase upon doping the As site by isovalent P, which acts as chemical pressure on EuFe_2As_2. Bulk superconductivity with transition temperatures of 22 K and 28 K are observed for x=0.16 and 0.20 samples respectively. The Eu ions order antiferromagnetically for x<=0.13, while a crossover is observed for x>=0.22 whereupon the Eu ions order ferromagnetically. Density functional theory based calculations reproduce the observed experimental findings consistently. We discuss in detail the coexistence of superconductivity and magnetism in a tiny region of the phase space and comment on the competition of ferromagnetism and superconductivity in the title compound.