• Subhash Chander

      Articles written in Pramana – Journal of Physics

    • Study of1840Ar ion tracks in cellulose nitrate

      Subhash Chander Shyam Kumar J S Yadav A P Sharma

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      Sample of cellulose nitrate (Russian) is exposed to1840Ar ions. The bulk etch rate has been studied at different etching temperatures and the activation energy for bulk etch rate has been calculated. The etched track lengths are measured for different etching times. The energy loss rate and range of1840Ar ions in CN(R) is also calculated. The critical threshold value for etchable track in CN(R) is determined by comparing the theoretical and experimental values of track length. The response curve of CN(R) is also presented.

    • Magnetic behaviour of nano-particles of Fe2.9Zn0.1O4

      Subhash Chander Sudhish Kumar Anjali Krishnamurthy Bipin K Srivastava V K Aswal

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      DC magnetization measurements are reported in the temperature range 20–100 K on a poly-disperse nano-particle sample of the spinel ferrite Fe2.9Zn0.1O4 with a log-normal size distribution of median diameter 43.6 Å and standard deviation 0.58. Outside a core of ordered spins, moments in surface layer are disordered. Results also show some similarities with conventional spin glasses. Blocking temperature exhibits a near linear variation with two-third power of the applied magnetic field and magnetizationM evolves nearly linearly with logarithm of timet. Magnetic anisotropy has been estimated by analysing theM-logt curve. Anisotropy values show a large increase over that of bulk particle samples. Major contribution to this enhancement comes from the disordered surface spins.

    • Magnetic behaviour of nano-particles of Fe2.8Zn0.2O4

      Subhash Chander Seema Lakhanpal Anjali Krishnamurthy Bipin K Srivastava V K Aswal

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      Magnetization measurements are reported on a nano-particle sample of Znsubstituted spinel ferrite Fe2.8Zn0.2O4 in the temperature range 20–300 K. Analysis of small-angle neutron scattering data shows the sample to have a log-normal particle size distribution of median diameter 64.4 Å and standard deviation 0.38. Magnetization evolves over a long period of timet going nearly linearly with logt. Magnetic anisotropy, estimated by fitting M-logt curve, shows many fold increase over that of bulk particle sample. Major enhancement owes to disordered moments in surface layer. In the nano-particle state as well increasing amount of Zn causes anisotropy to decrease.

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