Spin transitions of Co ions in RCoOsub(3) (R=Gd,Tb) investigated by measuring the electric field gradient at R and Co sites

Abstract

Hyperfine interactions in perovskite-structure RCoO3 (R=Gd,Tb) compounds have been measured by perturbed angular correlation technique using 111Cd and 181Ta nuclear probes. The electric quadrupole interactions at 111Cd show two different sites, assigned to probe substituting Gd or Tb and Co atoms. The temperature dependence of quadrupole frequencies shows discontinuities which have been interpreted as thermally activated spin-state transitions from low-spin ground state configuration to the intermediate-spin (IS) state and from IS state to high-spin state of Co3+ ion. For 181Ta only one major interaction was observed, which was assigned to probe at Co sites. Indication of a Jahn-Teller distortion, which stabilizes the intermediate-spin state with orbital ordering, is also pointed out.