ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Magnetic properties of binary and ternary mixed metal oxides NiFe₂O₄ and Zn_0.5Ni_0.5Fe₂O₄ doped with rare earths by sol—gel synthesis

Martin Tsvetkov, Maria Milanova, Laura C. J. Pereira, João C. Waerenborgh, Zara Cherkezova-Zheleva, Joana Zaharieva, and Ivan Mitov

Department of Inorganic Chemistry, Faculty of Chemistry and Pharmacy, Sofia University “St. Kliment Ohridski”, 1, J. Bourchier, 1164 Sofia, Bulgaria

E-mail: mariamilanova2@abv.bg, lpereira@ctn.tecnico.ulisboa.pt

Abstract: The spinel-type ferrites NiFe₂O₄ and Zn_0.5Ni_0.5Fe₂O₄ modified by lanthanide ions Eu³⁺ and Tb³⁺ were prepared by a sol-gel process with propylene oxide as a gelating agent. The phase homogeneity of the samples was tested by XRD and Mössbauer spectroscopy. Transmission electronic microscopy used for characterisation of the morphology of the samples revealed nanosized powdered samples with a narrow distribution of particle sizes. It was noted that the presence of Ln³⁺ ions influenced the magnetic properties of nanosized NiFe₂O₄ and Ni_0.5Zn_0.5Fe₂O₄ ferrites. The dependence of the magnetic properties of the samples on the rare-earth doping may be explained by the different grain sizes. The saturation magnetisation tends to decrease with increasing rare-earth doping and decreasing crystallite size. A similar trend was observed for the coercive field, with the exception of the Tb³⁺ -doped Zn_0.5Ni_0.5Fe₂O₄ where it remained the same as in the pure ferrite.

Keywords: ferrites; lanthanides; Mossbauer spectroscopy; XRD; magnetic properties

Full paper is available at www.springerlink.com.

DOI: 10.1515/chempap-2016-0097

Chemical Papers 70 (12) 1600–1610 (2016)