Study of hyperfine interactions in calcium titanate perovskite using TDPAC spectroscopy

Local electronic structure was investigated by observing hyperfine interactions (HFI) in Calcium titanate (CTO) perovskite using time differential perturbed angular correlation (TDPAC) spectroscopy. CTO was synthesized by gel-combustion method and doped with (¹⁸¹Hf/¹⁸¹Ta) TDPAC probe to study chemical environment around probe atom. Study revealed presence of two sites characterized by different quadrupole interaction frequencies, ω₁^a = 203 (2) and ω₁^b = 160 (2) Mrad/s, but with similar asymmetry parameters, η^a = 0.47 (0.01) and η^b = 0.47 (0.03). Electric Field Gradient (EFG) calculated from HFI parameters are 3.12 (0.03) and 2.47 (0.03) × 10²¹ V/m² for the two sites. Point charge model calculation concluded that the two sites have different EFG and corroborated the variation in EFG between two sites accurately. Plausible reasons for existence of two different HFIs at B-site of CTO perovskite is discussed.