Magnetic properties of barium borate glasses containing nickel micro-granules

Abstract

The EPR spectra of barium borate glasses containing 0.1, 0.25 and 0.4 wt.% nickel particles respectively have been investigated over the temperature range 77K to 300K. The magnetic susceptibility of these glasses has also been measured between 77K and 700K. Both sets of data indicate the presence of a broad range of transition temperatures below 300K. However, the mean transition temperatures as obtained by the two techniques are different. The results confirm a superparamagnetic behaviour exhibited by the fine nickel particles. The interaction energies between the particles and the transition temperatures have been calculated on the basis of the current model, and the discrepancy of the latter with experimental value is ascribed to the presence of a wide range of particle size.