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Nanocrystalline MnFe2O4 produced by niobium doping

Published online by Cambridge University Press:  31 January 2011

T. K. Kundu  and
D. Chakravorty
T. K. Kundu
Affiliation:
Indian Association for the Cultivation of Science, Jadavpur, Calcutta, 700 032, India
D. Chakravorty
Affiliation:
Indian Association for the Cultivation of Science, Jadavpur, Calcutta, 700 032, India, and Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, 560 064, India
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Abstract

Nanosized MnFe2O4 phase with diameters in the range 13.7 to 100 nm were produced by calcination and sintering treatments in the system zNb2O5 · (50 – z)MnO · 50Fe2O3 with z having values between 0 and 20. Nb5+ ions are believed to give rise to vacancies in the Mn2+ sites, which break up the coupling of ferrimagnetically active oxygen polyhedra. The Curie temperature decreases as the size of the MnFe2O4 phase is reduced. This is explained on the basis of a decrease in the number of exchange pairs of the type Mn2+–Fe3+. The coercivity increases with a decrease in the size of the ferrimagnetic phase. This is believed to arise due to a decrease in saturation magnetization as the size of the MnFeO4 phase is reduced.

Type
Articles
Information
Journal of Materials Research , Volume 14 , Issue 10 , October 1999 , pp. 3957 - 3961
Copyright
Copyright © Materials Research Society 1999

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