Distinct Suppression Mechanisms of Superconductivity by Magnetic Domains and Spin Fluctuations in EuFe2(As1-xPx)2 superconductors

Abstract

Using ac composite magnetoelectric technique, we map the phase diagrams of EuFe(As1-xPx)2 to resolve the interplay between superconductivity and ferromagnetism. For samples with Tc<TFM, the transition to a ferromagnetic multi-domain state suppresses Hc2 through the breakdown of Jaccarino-Peter compensation and enhanced magnetic scattering from inter-domain disorder, while Hirr is reduced due to vortex-antivortex pair nucleation at domain walls disrupting the vortex lattice. Conversely, for samples with Tc>TFM, strong short-range spin correlations and phase boundaries within a multiphase coexistence regime near the triple point act as potent pair-breaking centers, leading to pronounced Hc2 suppression.