The annealing kinetics of point defects which gave rise - in the presence of Ti4+-induced internal stresses - to pronounced, thermally activated magnetic after-effects near to 450, 200 and 65K in single-crystalline titanomagnetites Fe3-x-∆TixO4 of composition 0.1 < x < 0.3 and ∆ < 0.005 were considered. These relaxation processes were associated with reorientations of anisotropic point defect configurations of Ti4+-bound octahedral (B-site) vacancies (450K), Fe2+ interstitials (200K) and a specific mode of stress-reducing electron hopping (65K). In order to check the developed model conceptions, crystals were systematically annealed and the induced variations of the magnetic after-effect spectra carefully analysed with respect to the underlying defect kinetics. As an important result, the common recovery of the 450 and 200K magnetic after-effects, in one stage near T > 1000K, yielded coincident kinetics of reaction order 2 and recombination enthalpy Q = 2.45eV; compatible with bimolecular defect (vacancy) - anti-defect (interstitial) recombination. The delayed recovery of the 65K peak (at T ≥ 1100K) points to a stress-sensitive relaxation mechanism, being deactivated only with the final annihilation of stress-producing anisotropic defects.

Vacancy-Interstitial Annihilation in Titanomagnetite by Thermal Annealing. F.Walz, V.A.M.Brabers, J.H.V.J.Brabers, H.Kronmüller: Physica Status Solidi A, 2008, 204[10], 3514-25