• S K Kulshreshtha

      Articles written in Pramana – Journal of Physics

    • 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.

    • High pressure study of phase transitions inα-FePO4

      Chitra Murli Surinder M Sharma S K Kulshreshtha S K Sikka

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      High pressure behaviour of FePO4 in berlinite form has been investigated up to 10 GPa using vibrational Raman spectroscopy and energy dispersive x-ray diffraction. Combination of these techniques along with studies on pressure quenched samples reveal structural transitions in this material from its room pressure trigonal phase to a disordered and a crystalline phase near 3±0.5 GPa. The latter is the Cmcm phase which is the equilibrium structure at high pressures. These high pressure phases do not revert back to its initial structure after release of pressure. Irreversibility of these transformations indicates that FeO4 tetrahedra do not regain their initial coordination. These high pressure transitions can be rationalized in terms of the three level free energy diagram for such systems.

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