• R Jagannathan

      Articles written in Bulletin of Materials Science

    • A mössbauer study of hyperfine interactions in the boroferrite Fe3−xGaxBO6(x=0, 0·12)

      M Vithal R Jagannathan N Ravi

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      Fe3BO6 shows no thermal hysteresis around the phase transition temperatureTSR=418 K; Fe2·88Ga0·12BO6 undergoes spin transition atTSR=403 K resulting in a reduction of theTSR. Both these features are different from the reported observations on α-Fe2O3. The two Fe3+ sites show difference in their magnetic interactions. Ga3+ replaces Fe3+ in a random manner.

    • Spin-wave excitations in amorphous ferromagnets

      Anil K Bhatnagar B Bhanu Prasad N Ravi R Jagannathan

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      Mössbauer measurements have been performed on a number of metallic glasses. The temperature dependence of average hyperfine or internal magnetic fieldHeff(T) arises from long wavelength spin wave excitations in these glasses. Values ofB3/2 andC5/2 are in general much higher than those observed for crystalline ferromagnets indicating higher density of states for spin waves in amorphous ferromagnets.

    • Rare earth fluorescence in NASICON type phosphate glass, Na3TiZnP3O12

      G Vijaya Prakash P Nachimuthu M Vithal R Jagannathan

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      The emission spectra of Pr3+, Eu3+ and Dy3+ doped in NASICON type phosphate glass, Na3TiZnP3O12 (NTZP) are studied. The dopant rare earth ions occupy sites with 8–9 coordination in a highly covalent environment. For Pr3+ ion, calculated and observed branching ratios for lasing transitions3P03H4,6 agree well and found to be 0·64 and 0·24, respectively. The emissions of Pr3+ show strong temperature dependence on account of Boltzmann population of the higher excited states at room temperature. The excitation spectrum of Eu3+ gives rise to phonon assisted side band for5D27F0 transition at higher energy side with a phonon energy maximum of 1022 cm−1 and an electron phonon coupling strength (g) of 0·018. The value of phonon energy maximum agrees with infrared spectral data. The results show that observation of high energy emissions in phosphate glasses require much higherg values. The red/orange and yellow/blue transitions of Eu3+ and Dy3+, respectively show that the Eu3+ occupy more distorted site than Dy3+.

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