Neutron scattering study of the crystal electric field levels in an induced-moment spin-glass PrP0.9

Abstract

A neutron scattering study of the induced-moment spin-glass Pr${\mathrm{P}}_{0.9}$ has been performed and the results compared with a singlet ground-state stoichiometric sample Pr${\mathrm{P}}_{1.0}$. No magnetic order is observed in the polycrystalline samples down to $T=4.5\mathrm{}$ K. The ${\Gamma }_1-{\Gamma }_4$ crystalline electric field excitations observed in Pr${\mathrm{P}}_{1.0}$ are decreased by 10% in Pr${\mathrm{P}}_{0.9}$ which is in the opposite sense to that expected from changes in the lattice parameter. In addition, another broad excitation appears at low energies in Pr${\mathrm{P}}_{0.9}$ which probably plays a role in inducing moments on Pr sites. The random distribution of these moments reflects the random vacancy distribution, and they give rise to the observed spin-glass behavior. The temperature dependence of the quasielastic intensity measured at small momentum transfer, $Q=0.14\mathrm{}$ ${\mathrm{\AA }}^{-1\mathrm{}}$, exhibits a peak at $T\sim 8$ K which is in agreement with the bulk susceptibility measurements.