Thermal stability of nonmagnetic Cd and In impurities in Fe3O4.

Magnetite (Fe₃O₄) was doped with radioactive ^111mCd and ¹¹¹In ions as impurities, and their residence sites and thermal stability were investigated by means of time-differential perturbed angular correlation (TDPAC) spectroscopy. Well-defined TDPAC spectra unequivocally show their sites: Cd ions are stably located only in the tetrahedral A site in all the temperature range of the present observation (77 K-873 K); In ions also specifically occupy the A site at low temperature, but at high temperature part of them select the B site in a reversible fashion. The energy difference between the A and B sites for the accommodation of In was experimentally determined to be 0.119 (9) eV by assuming a Boltzmann distribution for the populations of the ¹¹¹In probe in the respective sites. The element-dependent thermal stabilities observed for Cd and In were well corroborated by density functional theory calculations. The successful observation of thermally activated site-tosite displacement of impurity In ions in Fe₃O₄ is reported. [ABSTRACT FROM AUTHOR]