Inhomogeneous level splitting in Pr$_{2-x}$Bi$_x$Ru$_2$O$_7$
  We report that Bi doping drives Pr$_x$Bi$_{2-x}$Ru$_2$O$_7$ from an antiferromagnetic insulator ($x=2$) to a metallic paramagnet ($x\approx 1$) with a broad low $T$ maximum in $C/T$. Neutron scattering reveals local low energy spin excitations ($\hbar\omega\approx 1$ meV) with a spectrum that is unaffected by heating to $k_BT>>\hbar\omega$. We show that a continuous distribution of splittings of the non-Kramers Pr$^{3+}$ ground state doublet such as might result from various types of lattice strain can account for all the data. 
J.van Duijn, K. H. Kim, N. Hur, D. Adroja, M. A. Adams, Q. Z. Huang,   M. Jaime, S. -W. Cheong, C. Broholm and T. G. Perring