Mössbauer-Effect Study of Calciomagnetites

S.M. Dubiela, J. Cieślaka, J. Orewczykb and S. Jasieńskab aFaculty of Physics and Nuclear Techniques, University of Mining and Metallurgy, Al. Mickiewicza 30, 30-059 Cracow, Poland bFaculty of Metallurgy and Material Engineering, University of Mining and Metallurgy, Al. Mickiewicza 30, 30-059 Cracow, Poland

Received: September 23, 1997; in final form January 28, 1998

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CaxFe3-xO4 samples, with x ≤ 0.28 , prepared from α-Fe2O3 and CaO by the Bridgman method were investigated by means of 57Fe 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, ⟨HB⟩/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 ⟨HB⟩ and the average isomer shift, ⟨IB⟩, 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.

DOI: 10.12693/APhysPolA.93.547 PACS numbers: 76.80.+y, 82.80.Ej