Abstract
The emission Mössbauer spectra of Co3−x O4 defect films are measured in external magnetic fields at strengths of 0.6–3.5 T. It is shown that the memory effect is observed in the spectra of Co3−x O4 defect films after exposure to an external magnetic field. At temperatures above the Néel temperature T N=26 K, the memory effect manifests itself in an increase in the relative contribution from the spectral line of the tetrahedral A sublattice in the spinel structure of Co3−x O4 crystallites ([Co 2+0.83 ]tetr[Co 3+2.20 ]octO4 and [Co 2+0.95 ]tetr[Co 3+2.10 ]octO4 prior to and after the magnetic field treatment, respectively). The isomer shifts δ and the quadrupole splitting ΔE of the spectral lines for both A and B sublattices also change from δA=−0.19 mm/s, δB=−0.31 mm/s, and ΔE B =0.83 mm/s to the values δA=−0.24 mm/s, δB=−0.33 mm/s, and ΔE B =0.60 mm/s, which are close to δ and ΔE for stoichiometric Co3O4 oxide. In the low-temperature spectra (T<T N), the memory effect additionally shows itself as a decrease in the hyperfine magnetic field H hf of the spectral component for the A sublattice as compared to that in the spectra measured prior to the magnetic field treatment. It is assumed that the concentration of cation vacancies decreases (and, correspondingly, the fraction of reduced Co2+ cations increases) in the Co3−x O4 defect films under the action of an external magnetic field. A possible mechanism of this process is proposed.
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Translated from Fizika Tverdogo Tela, Vol. 43, No. 7, 2001, pp. 1239–1246.
Original Russian Text Copyright © 2001 by Chibirova.
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Chibirova, F.K. Magnetic effects in Co3−x O4 defect films from the data of emission Mössbauer spectroscopy. Phys. Solid State 43, 1291–1298 (2001). https://doi.org/10.1134/1.1386468
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DOI: https://doi.org/10.1134/1.1386468