Point-defect interactions in electron-irradiated titanomagnetites--as analysed by magnetic after-effect spectroscopy...

During high-temperature growing of titanomagnetite single crystals (Fe(2.8-Δ)Ti(0.2)O(4), Δ < 0.005) in oxygen enriched atmospheres, specific Ti(4+)- and vacancy-based defect configurations are induced, giving rise to magnetic after-effect (MAE) spectra with peaks near 450, 200 and 65 K. The atomistic mechanisms of these relaxations are checked by exposing the crystals to low-temperature (80 K) electron (e(-)) irradiation and subsequent analysis of the interactions between radiation-induced and lattice-inherent defects on annealing over the range 80 K ≤ T(a) < or equal 1200 K. Within this interval, three characteristic temperature ranges are distinguished: (a) 80 K < T(a) < 500 K, revealing vigorous interactions between radiation-induced and inherent defect configurations, thus demonstrating their common point-defect nature; (b) 500 K < T(a) < 900 K wherein the MAE spectra re-assume, qualitatively, their initial structure with, however, mutually modified amplitude ratios; (c) 900 K < T(a) < 1200 K, being characterized by the complete annihilation of all MAEs but, interestingly, also the thermally induced re-appearance of vacancies and related defect configurations. The recovery kinetics of all prominent processes are numerically analysed and discussed with respect to their underlying atomistic mechanisms.