PAC study of CdFe2O4 and ZnFe2O4

The time-differential perturbed angular correlation technique has been used to study the temperature dependence of the electric-field gradient at ¹¹¹Cd nuclei in the spinels CdFe₂O₄ and ZnFe₂O₄. The samples were doped with radioactive ¹¹¹In tracers which decay to ¹¹¹Cd by electron capture. For both compounds the results of the measurements show the presence of two electric quadrupole interactions. One is well defined and corresponds to a fairly symmetrical electric field gradient. The other is broadly distributed and corresponds to electric field gradients with lower symmetry. The fractions of probes associated with these interactions are temperature dependent. The interactions are analysed taking into account the possible sites in the spinel structure for In occupation. The results are compared with those obtained with other spinels. The electric field gradient associated with the octahedral site is compared with the predictions of point charge model and with Mössbauer spectroscopy results at iron site.