Interplay of magnetism and superconductivity in EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ single crystals probed by muon spin rotation and ${}^{57}$Fe M\"ossbauer spectroscopy

TL;DR

This study investigates the magnetic and superconducting interplay in EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ single crystals using muon spin rotation and Mossbauer spectroscopy, revealing enhanced Eu fluctuations near the superconducting transition.

Contribution

It provides new insights into the coupling between Eu magnetism and Fe-based superconductivity through local probe measurements at optimal doping levels.

Findings

Enhanced spin dynamics in Fe sublattice above $T_{SC}$

Coupling between Eu fluctuations and Fe magnetic order

Superconductivity emerges above static Eu magnetic order

Abstract

We present our results of a local probe study on EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ single crystals with $x$=0.13, 0.19 and 0.28 by means of muon spin rotation and ${}^{57}$Fe M\"ossbauer spectroscopy. We focus our discussion on the sample with $x$=0.19 viz. at the optimal substitution level, where bulk superconductivity ($T_{\text{SC}}=28$ K) sets in above static europium order ($T^{\text{Eu}}=20$K) but well below the onset of the iron antiferromagnetic (AFM) transition ($\sim$100 K). We find enhanced spin dynamics in the Fe sublattice closely above $T_{\text{SC}}$ and propose that these are related to enhanced Eu fluctuations due to the evident coupling of both sublattices observed in our experiments.