Muon spin rotation and relaxation in Pr$_{1-x}$Nd$_x$Os$_4$Sb$_{12}$: superconductivity and magnetism in Pr-rich alloys

TL;DR

This study investigates the coexistence and suppression of superconductivity and magnetism in Pr$_{1-x}$Nd$_x$Os$_4$Sb$_{12}$ alloys using muon spin techniques, revealing weak Nd-spin coupling and the absence of spontaneous magnetic fields in Nd-doped samples.

Contribution

It provides new insights into the magnetic and superconducting properties of Pr-Nd alloy series, especially regarding the effects of Nd doping on time-reversal symmetry and magnetic ordering.

Findings

No spontaneous magnetic field in Nd-doped alloys for x > 0.05

Superfluid density remains unaffected by Nd concentration

Weak coupling between Nd spins and conduction electrons

Abstract

The Pr-rich end of the alloy series Pr$_{1-x}$Nd$_x$Os$_4$Sb$_{12}$ has been studied using muon spin rotation and relaxation. The end compound PrOs$_4$Sb$_{12}$ is an unconventional heavy-fermion superconductor, which exhibits a spontaneous magnetic field in the superconducting phase associated with broken time-reversal symmetry. No spontaneous field is observed in the Nd-doped alloys for x $>$ 0.05. The superfluid density is insensitive to Nd concentration, and no Nd$^{3+}$ static magnetism is found down to the lowest temperatures of measurement. Together with the slow suppression of the superconducting transition temperature with Nd doping, these results suggest anomalously weak coupling between Nd spins and conduction-band states.