• S K Paranjpe

      Articles written in Pramana – Journal of Physics

    • Non-spherical magnetic moment in MnAlGe

      S K Paranjpe S R Tendulkar L Madhav Rao N S Satya Murthy

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      The magnetic structure factors of MnAlGe (space groupP4/nmm) measured with polarised neutrons have been expressed in terms of the magnetic moment of the Mn atom (site symmetry tetrahedral with tetragonal distortion), the Bessel transforms 〈jn〉 of the Mn radial functions and the fractional occupancies of the moment density in the various crystal field orbitals. The measured structure factors were least-squares fitted with the theoretical expression involving 〈jn〉 appropriate to the Mn0, Mn+ and Mn2+ atoms. The best fit was got using Mn0 transforms, yielding 1·45µB as the Mn magnetic moment. The fractional occupancies of the moment density in the crystal field orbitalsA1g,B1gEg andB2g were obtained. This analysis shows the magnetic moment to be highly non-spherical with a large fractional occupancy (38%) in theA1g orbital directed along the tetragonal axis while the fractional occupancies ofB1g andB2g are found to be 31% and 30% respectively. The fractional occupancy of the moment in theEg orbital directed towards the Ge and Al atoms is very low (1%). The spatially averaged moment density of Mn in MnAlGe is more diffuse than that of Mn I and Mn II in isostructural Mn2Sb.

    • Neutron diffraction studies of transition metal nitrides

      N S Satya Murthy S K Paranjpe Marsongkohadi Kurniadi Sumaamidjaja M R L N Murthy

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      The magnetic structures of Fe4N and Mn4N have been redetermined using neutron diffraction. The magnetic form factors, obtained from polarised neutron data have been shown to be different for the face-centred and corner atoms. A qualitative explanation of the structures of Fe4N and Mn4N has been provided from the shapes of the magnetic form factors.

    • A neutron diffractometer with a linear position sensitive detector

      S K Paranjpe Y D Dande

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      A powder diffractometer with a linear position sensitive detector (PSD) has been designed and fabricated at BARC. The system is in operation at Dhruva reactor. The PSD has been tested for the position linearity and the uniformity of efficiency. The resolution Δd/d of the diffractometer has been found to be 1·3%. The data can be analyzed using profile refinement technique.

    • Magnetic behaviour of TbMnFe

      Keka Chakraborty S K Paranjpe V Siruguri O D Jayakumar S K Kulshreshtha

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      Neutron diffraction and Mössbauer measurements have been carried out on the cubic Laves phase intermetallic TbMnFe. The magnetic moment on the transition metal atom is found to be low, 0.2µB, at room temperature. This moment is temperature independent down to 10 K. Magnetic moment on the rare earth atom varies from 2.5µB at 296 K to 7.27µB at 10 K. Mössbauer spectra recorded at 298 K and 78 K have magnetic character but there is a large distribution of hyperfine field values. Both these features arise due to magnetic frustration created in the sample due to the competing ferro and antiferromagnetic interactions between the transition metal atoms.

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