• T T Srinivasan

      Articles written in Bulletin of Materials Science

    • The influence of Cu2+ substitution on the magnetic properties of Fe-Zn and Ni-Zn ferrites

      C M Srivastava M J Patni G Srinivasan T T Srinivasan

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      The influence of a Jahn-Teller ion on magnetization,g-values and linewidth in Znx Fe3−xO4 and Ni1−x Znx Fe2O4 spinel ferrites has been investigated by introducing small quantities of Cu2+ ions. The magnetization of Cu substitution in both the systems but the curie temperature is affected only in FeZn ferrites. The lattice constant in NiZn is significantly reduced while in FeZn there is only a slight increase. The change ingeff on copper substitution,Δgeff, is very different in the two systems. In NiZn,Δgeff has a uniform value, ∼ 0·2, for all values ofx while in FeZn it has a peak atx=0·3 and vanishes atx=0 andx⩾0·5. The ferromagnetic linewidthΔH does not change significantly on copper substitution in both the systems. An explanation based on the perturbation produced due to the local lattice distortion by the Jahn-Teller mechanism explains the observed results satisfactorily.

    • Infrared absorption in spinel ferrites

      T T Srinivasan C M Srivastava N Venkataramani M J Patni

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      Their spectra of a number of ferrites, MFe2O4, M(Mn, Fe, Co, Ni, Cu and Zn) have been studied at room temperature in the range 200–1000 cm−1. In all the cases the spectrum consists of four bands, two of which have strong absorption while the other two have weak absorption and often appear as shoulders on the main band. However up to 20% of the inverse ferrite, the shoulder in the low energy side appears as a band. In this paper we have analysed the origin of the above bands.

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