• S K Paranjpe

      Articles written in Pramana – Journal of Physics

    • Magnetic structure of (Fe0.97Cr0.03)2P

      Sudhish Kumar S K Paranjpe Bipin K Srivastava Anjali Krishnamurthy V C Sahni

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      Magnetic behaviour of di-metal iron phosphide with a small substitution of iron by chromium, (Fe0.97Cr0.03)2P, has been studied using SQUID magnetometry and powder neutron diffraction. It is paramagnetic at temperatures above ∼180 K with persisting short range ferromagnetic (FM) order. At lower temperatures three different regions of magnetic behaviour are identified. FM order evolves in the region 180 K-120 K but much more slowly and with much less magnetic moments than in Fe2P. In the region 120 K-50 K negative exchange interactions gain some importance leading to a loss of FM order. Below 50 K FM interactions again dominate. Pinning centres influence the behaviour at low temperature up to ∼100 K.

    • Structural study and electrical properties of Zr-doped Nd2Sn2O7 pyrochlore compounds

      Y D Kolekar S B Kulkarni Keka Chakraborty A Das S K Paranjpe P B Joshi

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      Nd2Sn2O7 pyrochlores with the substitution of Zr4+ were prepared by conventional ceramic double sintering technique. The single-phase formation was confirmed by X-ray diffraction and neutron diffraction techniques. Relative intensity calculations for X-ray diffraction analysis were performed for oxygen positional parametersx = 0.331 and 0.375, while Rietveld refinements were employed for neutron diffraction data. The neutron diffraction study revealed that there are only two anion sites with 48f and 8b positions. This indicates that the 8a site, i.e. O(3) sublattice, is completely vacant and the structure is a perfect cubic pyrochlore with space group Fd3m (Oh7). From the conductivity measurements, it is observed that the electronic conductivity dominates from room temperature up to about 525 K and forT > 525 K, the oxygen ion conduction dominates the charge transport in these compositions. Complex impedance spectroscopy indicates the existence of grain and grain boundary as two separate elements.

    • Magnetization and neutron diffraction studies on FeCrP

      Sudhish Kumar Anjali Krishnamurthy Bipin K Srivastava A Das S K Paranjpe

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      Crystal structure and magnetic behaviour of FeCrP have been investigated using magnetization and neutron diffraction measurements. FeCrP crystallizes in orthorhombic FeZrP type structure (Pnma space group,Z = 4) in which Cr atoms occupy the pyramidal site and Fe atoms occupy the tetrahedral site with total preference. Structural parameters including positional parameters have been refined. The refined values of positional parameters for Fe and Cr are quite different from those in FeZrP. The nature of magnetization-temperature curve is suggestive of antiferromagnetic nature withTN = 280 (±10) K. Preliminary analysis of neutron diffraction pattern at 13 K is indicative of a rather complicated magnetic structure.

    • Magnetic behaviour of (Fe0.85Cr0.15)2As

      S K Jain A Das Bipin K Srivastava Anjali Krishnamurthy S K Paranjpe

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      Magnetization and neutron diffraction measurements have been made on the title pseudo-binary of tetragonal anti-ferromagnets Fe2 As and Cr2 As. In this system antiferromagnetic (AFM) ordering appears below 310 K. The moments are confined in theab plane but unlike in the end members they are tilted off thea-axis. In addition to the AFM structure a weak ferromagnetic behaviour shows up below∼80 K with a rather low moment of ∼0.07 μB per formula unit at 5 K and under a field of 3 T.

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