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"Ni- and Zn-doped hematite obtained by combustion of mixed metal oxinates"
C.A. Barrero, J. Arpe, E. Sileo, L.C. Sánchez, R. Zysler and C. Saragovi
Proc. of the Workshop "At the Frontiers of Condensed Matter II - Magnetism, Magnetic Materials, and their Applications", Buenos Aires, Argentina, June 22-26, 2004. Ed. C. Saragovi, J. Guevara, R. Weht, A.M. Llois and M.T. Causa
Physica B Condens. Matter. 354(1-4) (2004) 27-34
We have studied the changes in the structural and magnetic properties of hematite obtained by a new method based on the combustion of mixed Fe(III)0.95, Ni(II)0.05- and Fe(III)0.95, Zn(II)0.05-oxinates. Thermogravimetric analysis shows that the decomposition of the mixed oxinates proceeds in an overall weight loss formed at least by two stages and the weight loss is related to the formation of probably CO2, N2 and H2O, and a solid residue. X-ray diffraction and Mössbauer spectroscopy reveal that the residue of the thermally treated Fe(III)0.95, Zn(II)0.05-oxinate is α-Fe2O3 and ZnFe2O4, whereas in the case of Fe(III)0.95, Ni(II)0.05-oxinate is Ni-doped α-Fe2O3 and NiFe2O4. Results suggest low Ni incorporation into the hematite structure. However, it was difficult to establish if Zn-for-Fe substitution in hematite had taken place. The comparison between the two hematites obtained in this work with a non-doped one shows reduction in the cell parameters, increment in the saturation hyperfine fields, and reduction in the Néel temperatures. The presence of the dopant, vacancy sites and lattice distortion are responsible for these effects.
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