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Mössbauer-Effect Study of Calciomagnetites

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Dubiel S., Cieślak J., Orewczyk J., Jasieńska S.

Acta Physica Polonica A

1998

vol. 93

issue 3

547-561

Ca_{x}Fe_{3-x}O_{4} samples, with x ≤ 0.28 , prepared from α-Fe_{2}O_{3} and CaO by the Bridgman method were investigated by means of ^{57}Fe Mössbauer spectroscopy. Room temperature spectra gave evidence that the samples were multiphase, the calciomagnetite being the dominant phase with a contribution of 73% to 99%, depending on the sample. Analysis of the subspectra associated with the calciomagnetite gave evidence that Ca-ions reside on the tetrahedral (A) sites and have not random distribution. Their presence on those sites causes a reduction of the hyperfine field at Fe nuclei occupying the octahedral positions (B) by 12.3(1.0) kOe per one Ca-ion and a decrease in the average hf field, 〈H_{B}〉/dx, at the rate of 29 kOe/mol% for x ≤ 0.07 and of 387 kOe/mol% for larger x. In addition, a linear correlation between 〈H_{B}〉 and the average isomer shift, 〈I_{B}〉, was revealed to hold. It indicates that addition of Ca-ions into the magnetite causes a decrease in the spin-density and an increase in the charge-density at Fe nuclei occupying the B-sites.

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1 Acta Physica Polonica A

1 1998

1 Cieślak J.

1 Dubiel S.

1 Jasieńska S.

1 Orewczyk J.

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Mössbauer-Effect Study of Calciomagnetites