Positron and Positronium Annihilation as Probes to Identify Cation Substitution Effects in CoCrxFe2-xO4

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CoCrxFe2-xO4 samples with x = 0.0 to 2.0 were prepared by air oxidation of aqueous suspension containing Co2+, Cr3+ and Fe3+ ions and characterized by x-ray diffraction. Positron lifetime and coincidence Doppler broadening (CDB) measurements indicated three distinct stages of positron trapping in defects. Initially the vacancy-type defects located at the A-sites (tetrahedral) trapped positrons but, with the substitution of Fe by Cr in low concentrations (x <= 0.7), positrons are trapped by defects at the B-sites (octahedral). Mossbauer spectroscopic results indicated the cationic distribution at B-sites to be stoichiometry-dependent and, till x = 0.7, the deficiency of Fe3+(B) ions was compensated by interchange of Fe3+(A) ions with Co2+(B) ions. Between x = 0.9 and 1.7, the substitution resulted in continued decrease of Fe3+(B) ions and the structure got fully transformed into a normal spinel configuration during x = 1.8 to 2.0.

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Edited by:

Jozef Krištiak, Jan Kuriplach and Pradeep K. Pujari

Pages:

215-218

Citation:

P.M.G. Nambissan et al., "Positron and Positronium Annihilation as Probes to Identify Cation Substitution Effects in CoCrxFe2-xO4", Materials Science Forum, Vol. 733, pp. 215-218, 2013

Online since:

November 2012

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[1] J. Smit and and H. P. J. Wijn: Ferrites—Physical Properties of Ferrimagnetic Oxides in Relation to Their Technical Applications (N. V. Philip's Gloeilampenfabrieken, Holland, Eindhoven 1959).

[2] F. Scordari, in : Fundamentals of Crystallography, edited by C. Giacovazzo, Oxford University Press, New York (1992), p.403.

[3] J.V. Olsen, P. Kirkegaard, N.J. Pedersen and M. Eldrup: Phys. Stat. Sol. (c) Vol. 4 (2007), p.4004.

[4] P. Asoka-Kumar, M. Alatalo, V. J. Ghosh, A. C. Kruseman, B. Nielsen and K. G. Lynn: Phys. Rev. Lett. Vol. 77 (1996), p. (2097).

DOI: https://doi.org/10.1103/physrevlett.77.2097

[5] T. Koida, S.F. Chichibu, A. Uedono, A. Tsukazaki, M. Kawasaki, T. Sota, Y. Segawa and H. Koinuma : Appl. Phys. Lett. Vol. 82 (2003), p.532.

DOI: https://doi.org/10.1063/1.1540220

[6] S. Bandyopadhyay, A. Roy, D. Das, S.S. Ghugre and J. Ghose : Philos. Mag. Vol. 83 (2003), p.765.

[7] M. Noguchi, M. Takefumi, C. Toshinobu, T. Takaho and T. Nobuo : J. Phys. Soc. Japan Vol. 32 (1972), p.1242.

[8] B. Bergersen and M.J. Stott : Solid State Commun. Vol. 7 (1969), p.1203.

[9] H. Mohan, I.A. Shaikh and R.G. Kulkarni : Physica B Vol. 217 (1996), p.292.

[10] http: /chemistry. about. com/library/blperiodictable. htm.

[11] S. Chakraverty, Subarna Mitra, K. Mandal, P. M. G. Nambissan and S. Chattopadhyay: Phys. Rev. B Vol. 71 (2005), p.024115.