Timescale settling and nature of electron transport in magnetite - general considerations in view of new magnetic aftereffect results on dilutely Ti4+-doped Fe3O4

The effect of dil. titanium (Ti4+)-doping on the magnetic after-effect (MAE) spectra of stoichiometric magnetite single crystals, Fe3-xTixO4 - with 0.0001 ? x ? 0.008 - was studied in the temp. range 4 K <T ? TV .simeq. 125 K and analyzed in terms of the authors' revised relaxation model. The effects of these relatively low doping rates comprise: (i) strong impact on low-temp. (4 K <T <35 K) incoherent electron (e-)-tunneling and combined intraionic thermal excitation; (ii) minor, though highly instructive, modifications of thermally activated electron hopping (50 K <T <125 K), and (iii) low-temp. shifting of the Verwey transition (TV) relative to the temp. of zero-crossing of the crystal anisotropy (TK1). Due to the high oxygen stoichiometry of the crystals (absence of B-site vacancies), no further MAEs appear in the high-temp. range (T > TV). The recently accentuated discussion concerning the appropriate timescale of electron transport - deduced from modern x-ray resonant scattering to be about t .simeq. 10-16 s, over the whole temp. range (T [symbol omitted] TV), in contrast to up to thousands of seconds as detd. from high-precision MAE expts., in the low-temp. phase (T <TV) - gives the authors the chance to sharpen the authors' arguments in favor of a clarification of the electronic cond. mechanisms in magnetite. [on SciFinder (R)]