J. Phys. IV France 08 (1998) Pr2-351-Pr2-354
Magnetic disaccommodation in Sr doped magnetiteP. Hernández Gómez1, C. de Francisco1, J.M. Muñoz1, O. Alejos1, C. Torres1 and M. Zazo2
1 Departamento Electricidad y Electrónics, Facultad de Ciencias, Universidad de Valladolid, Prado de la Magdalena, s/n, 47071 Valladolid, Spain
2 Departamento Física Aplicada, Facultad de Física, Universidad de Salamanca, 37071 Salamanca, Spain
The relaxation of the initial permeability is rneasured in polycrystalline strontium doped magnetite with initial compositions SrO nFe2O3, wth n ranging between n=16 and n-122.34. The samples have been sintered at 1300° C in a reducing CO2 atmosphere and rapidly quenched to provide the presence of crystal vacancies. In the temperature range between 80 and 500 K, the tltne decay of the initial after sample demagnetization is represented by means of isochronal curves. The behavior is similar to a previous study dealing with barium doped rnagnetite, i.e., the existence of two relaxation peaks centered at temperatures of 300 and 365 K. These relaxation processes are related with thermally activated jumps of ferrous cations into lattice vacancies. However, it's noteworthy to point to the existence of some differences. As we can see in the maxima of the isochronal spectra, a new peak appears at temperatures close to 160 K, only when there is at least a certain amount of strontium in the initial composition (n < 39.95). This new peak appears also in compounds with the hexagonal SrM-phase studied elsewhere and is explained in terms of the formation of a secondary phase with hexagonal structure.
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