Analysis of Magnetic After-Effect Spectra in Titanium-Doped Magnetite

The magnetic after-effect (MAE) spectra of titanomagnetites, Fe3—x—ΔTixO4, with constant vacancy content, Δ ≈︂ 10—4, and systematically varied Ti4+-substitutions, 0.01 ≤ x ≤ 0.4, are thoroughly analyzed in the temperature range 4 K < T < 460 K. These spectra are characteristically modified in the presence of already small Ti4+-substitutions (x ≥ 0.01): (i) the order-dependent, low-temperature (T < 125 K) electronic relaxations are severely affected; (ii) the ionic, vacancy-mediated process III1, 2 (300 K) splits up into two satellites III* (260 K) and II1, 2 (around 400 K); (iii) near 200 K, additionally process IV1, 2 develops which is deduced to be of interstitial type. In terms of plausible models, the mechanisms and respective interrelations of these various processes are clearly revealed and their activation parameters numerically determined.