Influence of stoichiometry on the magnetic disaccommodation in barium M-type hexaferrites.

The time decay of the relative initial magnetic permeability after sample demagnetization has been measured in the temperature range 80K < T < 420K in series of samples with initial composition BaO·nFe₂O₃ (n = 5.7, 6 and 6.3), i.e. the stoichiometric M-type barium ferrite and compositions with excess and defect of iron. These samples have been sintered under different conditions of temperature and partial oxygen pressure. The results have been represented by means of isochronal curves. We have observed that the behaviour changes drastically with the sintering atmosphere, and the results with less iron are qualitatively different from the others when sintering in air. The underlying mechanisms responsible for the relaxation phenomena observed are pointed out in terms of the formation of different hexagonal phases. [ABSTRACT FROM AUTHOR]