• R Nagarajan

      Articles written in Bulletin of Materials Science

    • Mossbauer and magnetic studies on the system Fe3−xTixO4

      R Nagarajan C R K Murty

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      Mossbauer measurements have been made on the system Fe3−xTixO4 for 1·0 ≥x ≥ 0. This system is interesting in that it is expected to form a continuous solid solution over the whole range and also occurs naturally. Spectra taken at various temperatures between 300 K and 77 K show complex behaviour. The results can be understood in terms of disorder and consequent formation of superparamagnetic clusters which are supported by our earlier hysteresis and susceptibility studies at various temperatures. It appears that with increasing Ti content domain wall formation is inhibited resulting in effectively monodomain clusters. Considering the work reported by others, we suggest that Mossbauer spectra of multidomain material should show well-resolved magnetic hyperfine spectrum, even close to itsTN.

    • 151Eu Mössbauer studies on Zn-doped EuBa2Cu3O7−y

      C V Tomy R Nagarajan S K Malik Ram Prasad N C Soni Kalyan Adhikary

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      151Eu Mössbauer studies have been performed on the compounds EuBa2(Cu1−xZnx)3O7−y withx=0·0, 0·025, 0·05, 0·075 and 0·1. The parent compound, EuBa2Cu3O7−y is superconducting with a transition temperature (Tc) of 88 K.Tc is depressed as Zn is substituted for Cu in this system and the compounds withx>0·05 do not show superconductivity down to 12 K.151Eu Mössbauer studies at 295 K show a single Mössbauer line in all the compounds (whether superconducting or not) with isomer shift value typical of Eu3 + ion. Further, the isomer shift values are nearly independent ofx and the temperatures down to 10 K. These observations imply that the Cu-O network responsible for superconductivity is very weakly coupled to the Eu sublattice.

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