• R V Upadhyay

      Articles written in Pramana – Journal of Physics

    • Magnetic properties of ultra-fine particles of Mn0.5Fe0.5Fe2O4 spinel system

      R V Upadhyay R V Mehta

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      A systematic study of the magnetic properties of ultra-fine particles of Mn0.5Fe0.5Fe2O4 spinel system has been undertaken. The effect of temperature on the magnetic properties of particles and the ferrofluid has been studied. Analysis of the data yields information on the anisotropy constant, particle size distribution and superparamagnetic behaviour. The results are explained on the basis of existing theories.

    • Temperature dependence electron spin resonance spectra of a magnetic fluid

      R V Upadhyay D Srinivas R V Mehta P M Trivedi

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      ESR spectra of a laboratory synthesized kerosene base magnetic fluid containing ultrafine magnetic particles (average diameter of 100A) of Zn0.1 Fe0.9Fe2O4 are recorded at different temperatures. A narrow signal was observed above the melting point of the carrier liquid (200 K) which can be attributed to a very small volume fraction of superparamagnetic particles in the system. The peak-to-peak line width for both low and high field cooled configurations show an increase with decreasing temperature. This observed behaviour has been explained by considering various energy terms which contribute to the line width.

    • Time dependent magnetization of a Zn0.1Fe0.9Fe2O4 fine magnetic particle system

      R V Upadhyay

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      The time dependent magnetization measurements of the fine particles (100Å) of Zn0.1Fe0.9Fe2O4 ferrite system at 68 K are reported. The time decay of magnetization is found to be logarithmic. The time dependent co-efficient varies with the applied field and is maximum at coercive field. The value of anisotropy obtained from the variation of time dependent co-efficient with field agrees well with earlier results.

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