Point-defect interactions in electron-irradiated titanomagnetites—asanalysed by magnetic after-effect spectroscopy on annealing within80 K < Ta < 1200 K

Abstract

During high-temperature growing of titanomagnetite single crystals (Fe2.8−ΔTi0.2O4,Δ < 0.005) in oxygen enrichedatmospheres, specific Ti4+- 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 theserelaxations are checked by exposing the crystals to low-temperature (80 K) electron (e−) irradiation and subsequent analysis of the interactions between radiation-induced andlattice-inherent defects on annealing over the range K.Within this interval, three characteristic temperature ranges are distinguished: (a) 80 K < Ta < 500 K, revealing vigorous interactions between radiation-induced and inherent defectconfigurations, thus demonstrating their common point-defect nature; (b) 500 K < Ta < 900 K wherein the MAE spectra re-assume, qualitatively, their initialstructure with, however, mutually modified amplitude ratios; (c) 900 K < Ta < 1200 K, being characterized by the complete annihilation of all MAEs but, interestingly, also thethermally induced re-appearance of vacancies and related defect configurations.The recovery kinetics of all prominent processes are numerically analysed and discussedwith respect to their underlying atomistic mechanisms.