Muon-spin relaxation studies of weak magnetic correlations in U1-xThxBe13.

Abstract

Zero-field positive muon-spin relaxation rates in ${\mathrm{U}}_{0.965}$${\mathrm{Th}}_{0.035}$${\mathrm{Be}}_{13}$ provide definitive evidence for the onset of magnetic correlations at the lower phase transition at temperature ${T}_{c2}$ below the normal-superconducting transition at ${T}_{c1}$. The transition at ${T}_{c2}$ is found to be second order and mean field like, with a moment (${10}^{\mathrm{\ensuremath{-}}3}$\char21{}${10}^{\mathrm{\ensuremath{-}}2}$)${\ensuremath{\mu}}_{B}$/f atom. Candidates for the second phase, such as magnetic order and magnetic superconducting states, are discussed.