Short-range antiferromagnetic correlations in the superconducting state of filled skutterudite alloys Pr$_{1-x}$Eu$_x$Pt$_4$Ge$_{12}$

TL;DR

This study investigates how Eu substitution affects superconductivity and magnetic correlations in filled skutterudite alloys, revealing short-range antiferromagnetic correlations in the superconducting state and AFM ordering at higher Eu concentrations.

Contribution

It provides experimental evidence and theoretical modeling of short-range antiferromagnetic correlations coexisting with superconductivity in Eu-doped skutterudite alloys.

Findings

Eu doping suppresses superconducting transition temperature.

Schottky peaks indicate internal magnetic fields due to Eu moments.

Short-range AFM correlations are present in the superconducting state.

Abstract

Motivated by current research efforts towards exploring the interplay between magnetism and superconductivity in multiband electronic systems, we have investigated the effects of Eu substitution through thermodynamic measurements on the superconducting filled skutterudite alloys Pr$_{1-x}$Eu$_x$Pt$_4$Ge$_{12}$. An increase in Eu concentration leads to a suppression of the superconducting transition temperature consistent with an increase of magnetic entropy due to Eu local moments. While the low-temperature heat capacity anomaly is present over the whole doping range, we find that in alloys with $x\leq0.5$ the Schottky peaks in the heat capacity in the superconducting state appear to be due to Zeeman splitting by an internal magnetic field. Our theoretical modeling suggests that this field is a result of the short-range antiferromagnetic correlations between the europium ions. For the samples with $x > 0.5$, the peaks in the heat capacity signal the onset of antiferromagnetic (AFM) ordering of the Eu moments.