Inhomogeneous level splitting in Pr${}_{2-x}$Bi${}_x$Ru${}_2$O${}_7$

Abstract

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 ($\hslash \ddot{I}‰\approx 1$ meV) with a spectrum that is unaffected by heating to $k_{B}T>>\hslash \ddot{I}‰$. 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.

4 pages and 4 figures