Muon spin rotation and relaxation in Pr1−xNdxOs4Sb12 : Superconductivity and magnetism in Pr-rich alloys

Abstract

The Pr-rich end $0\ensuremath{\le}x\ensuremath{\le}0.25$ of the alloy series ${\mathrm{Pr}}_{1\ensuremath{-}x}{\mathrm{Nd}}_{x}{\mathrm{Os}}_{4}{\mathrm{Sb}}_{12}$ has been studied using muon spin rotation and relaxation. The end compound ${\mathrm{PrOs}}_{4}{\mathrm{Sb}}_{12}$ is an unconventional heavy-fermion superconductor, which exhibits a spontaneous magnetic field associated with broken time-reversal symmetry (TRS) in the superconducting phase. No such field is observed in the Nd-doped alloys for $x\ensuremath{\ge}0.05$, indicating that TRS has been restored. The superfluid density from the vortex-lattice field distribution is insensitive to Nd concentration for $x\ensuremath{\lesssim}0.2$, indicating that TRS restoration does not have a strong effect on the superconducting state. No ${\mathrm{Nd}}^{3+}$ static magnetism, ordered or disordered, is found down to the lowest temperatures of measurement.