The synthesis and magnetic properties of a nanostructured Ni-MgO system
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We have investigated the magnetic properties of the Ni-MgO system with an Ni concentration of 0.5 at.%. In asgrown crystals, Ni ions occupy substitutional Mg sites. Under these conditions the Ni-MgO system behaves as a perfect paramagnet. By using a controlled annealing treatment in a reducing atmosphere, we were able to induce clustering and form pure Ni precipitates in the nanometer size range. The size distribution of precipitates or nanodots is varied by changing annealing time and temperature. Magnetic properties of specimens ranging from perfect paramagnetic to ferromagnetic characteristics have been studied systematically to establish structure-property correlations. The spontaneous magnetization data for the samples, where Ni was precipitated randomly in MgO host, fits well to Bloch’s T3/2-law and has been explained within the framework of spin wave theory predictions.
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