ON THE ANNEALING OF MAGNETIC RELAXATIONS IN MAGNETITE AT HIGH-TEMPERATURES .1. A NEW LOOK AT THE ROOM-TEMPERATURE RELAXATION

In this work we present a detailed analysis of the annealing behaviour of the MAE in ceramic samples of vacancy doped magnetite Fe3-deltaO4. The samples were annealed in the temperature range 400 < T(K) < 800 a nd we have centred our analysis on the relaxation process encountered in the temperature range 250 < T(K) < 350 (peak III). We observed that in the first annealing stages, peak III is composed of at least two r elaxation processes which we attribute to the presence of single vacan cies and their complexes. These complexes are very unstable and dissoc iate in the first annealing stages. In the final annealing steps, we a re left with only octahedrally coordinated single vacancies that migra te with activation parameters Q almost-equal-to 0.85 eV, tau0 almost-e qual-to 10(-13) s and DELTAQ almost-equal-to 0.08 eV. From an analysis of our annealing curves we conclude that the main annealing process i s the movement of vacancies to the grain boundaries.