Temperature dependence of electric field gradient in TbCoO3

Abstract

The temperature dependence of the electric field gradient (efg) in TbCoO3 perovskite was measured by perturbed angular correlation (PAC) technique using 111Cd and181Ta nuclear probes. The radioactive parent nuclei 111In and 181Hf were introduced into the compound through a chemical process during sample preparation. The electric quadrupole interactions at 111Cd show two different sites, assigned to probe substituting Tb and Co atoms. The temperature dependence of quadrupole frequencies show sharp discontinuities which have been interpreted as thermally activated spin state transitions from low-spin ground state configuration to the intermediate-spin state and from intermediate-spin to high-spin state of Co3 + ion. For 181Ta only one interaction was observed, which was assigned to probe at Co site. Indication of a Jahn–Teller distortion, which stabilizes the intermediate-spin state with orbital ordering, is also pointed out. No magnetic order was observed till 77 K.