• P A Joy

      Articles written in Bulletin of Materials Science

    • Comparison of the irreversible thermomagnetic behaviour of some ferro- and ferrimagnetic systems

      P S Anil Kumar P A Joy S K Date

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      The magnetic behaviour of two ferromagnetic oxides and two ferrimagnetic oxides (ferrites) are compared to study the effect of magnetocrystalline anisotropy on thermal-history-dependence of magnetization of these ordered magnetic systems. All four compounds show thermomagnetic irreversibility (MFC >MZFC) below a certain temperature,Tirr. The highly anisotropic ferromagnetic oxide, SrRuO3 and the hard ferrite, SrFe12O19 show sharp peaks belowTc in theirMZFC(T) curves, whereas for the soft ferrite Ni0.8Zn0.2Fe2O4 and the low anisotropic ferromagnetic oxide La0.7Ca0.3MnO3 only a broad maximum is observed inMZFC, when measured in small magnetic fields. The shapes of theMZFC(T) curves are inversely-related to the magnitude of the coercivities (Hc) of the compounds in relation to the applied field, and the temperature dependence of Hc.MFC andMZFC are related through the coercivity for all four magnetic systems.

    • Tailoring magnetic and dielectric properties of rubber ferrite composites containing mixed ferrites

      M R Anantharaman K A Malini S Sindhu E M Mohammed S K Date S D Kulkarni P A Joy Philip Kurian

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      Rubber ferrite composites containing various mixed ferrites were prepared for different compositions and various loadings. The magnetic and dielectric properties of the fillers as well as the ferrite filled matrixes were evaluated separately. The results are correlated. Simple equations are proposed to predetermine the magnetic and dielectric properties. The validity of these equations is verified and they are found to be in good agreement. These equations are useful in tailoring the magnetic and dielectric properties of these composites with predetermined properties.

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