• S N Shringi

      Articles written in Bulletin of Materials Science

    • Influence of the presence of Fe2+ ion in nickel-zinc ferrite

      C M Srivastava S N Shringi M J Patni S M Joglekar

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      The presence of small amounts of Fe2+ ion in nickel zinc ferrite significantly influences some of its magnetic properties. The lattice parameter increases slightly and the increase Δa is independent ofx. The variation of magnetization with zinc concentration is explained on the basis of the Yafet-Kittel model. Increase in the Néel temperature on Fe2+ substitution in ZnxNi1-xFe2O4 is remarkable. This has been explained on the basis of a four sublattice model. Our analysis shows thatJAB (d5-d5) interaction is most affected. The influence of Fe2+ ions on the relaxation processes in the Mössbauer line shapes of Ni-Zn ferrite is also investigated and is compared with Cu2+ doped Ni-Zn ferrite.

    • Mössbauer spectroscopy of titanium-substituted iron garnets

      C M Srivastava S N Shringi B Uma Maheshwar Rao D Bahadur Om Parakash

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      The Mössbauer spectroscopy of polycrystalline Y3−xCaxFe5−xTixO12 (x=0·2, 0·5, 0·7) garnets has been studied at room temperature. The hyperfine fields both at the octahedral and tetrahedral sites decrease with increasing titanium content. The hyperfine fields both ata andd-sites are linearly proportional to magnetization. The quadrupole splitting fora-site shows no dependence on Ti content while the quadrupole splitting ford-site increases slightly withx. The results are explained on the basis of lattice distortion due to Ti substitution ona-site.

    • Magnetic structure of zinc ferrite

      C M Srivastava S N Shringi M Vijaybabu

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      A detailed analysis of the available experimental data has been made for the ordered phase of ZnFe2O4. The abnormally lowTN and the observed spin arrangement have been explained on the basis of the hybridization of orbitals on the oxygen ions which gives rise to an anisotropic exchange interaction. The variation of hyperfine field and susceptibility with temperature along with the zero point reduction of the magnetic moment indicate that the ZnFe2O4 is a two-dimensional antiferromagnet.

    • Development of pure and doped gamma ferric oxide

      M R Anantharaman K Seshan S N Shringi H V Keer

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      Optimum conditions and experimental details for the formation of γ-Fe2O3 from goethite have been worked out. In another method, a cheap complexing medium of starch was employed for precipitating acicular ferrous oxalate, which on decomposition in nitrogen and subsequent oxidation yielded acicular γ-Fe2O3. On the basis of thermal decomposition in dry and moist nitrogen,dta, xrd, gc and thermodynamic arguments, the mechanism of decomposition was elucidated. New materials obtained by doping γ-Fe2O3 with 1–16 atomic percent magnesiu, cobalt, nickel and copper, were synthesised and characterized.

    • Mössbauer study of 3d-ion-substituted YBa2(Cu, Fe, M)3O7−δ; M=V, Mn

      S N Shringi R V Vadnere O M Prakash

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      57Fe Mössbauer investigations at 300K have been carried out on V,Mn substituted YBa2Cu3O7−δ system. Preliminary studies show that for small concentration of V (4%), Fe occupies preferentially the Cu(1) site whereas for the same concentration of Mn, Fe prefers the Cu(2) site. It is suggested that for low concentrations V has a preference for Cu(2) site whereas Mn prefers Cu(1) site in the 1-2-3 lattice.

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