Spin-Freezing Temperature of Some Oxide and Fluoride Glasses Containing Iron (III)

Abstract

The magnetic transition observed in iron-containing oxide and fluoride glasses where antiferromagnetic interactions are dominant among the iron ions has been discussed on the basis of the superparamagnetic model. The theoretical approach based on the model proposed by Shtrikman and Wohlfarth has revealed that the spin-freezing temperature of the oxide and fluoride glasses increases with the increase of the average value of the superexchange interaction. This suggests that the spin-freezing temperature increases with the increase of the covalency of Fe-O or Fe-F bond when the content of the iron ions is identical. The relation between the spin-freezing temperature and the isomer shift value obtained experimentally for some oxide and fluoride glasses seems to support this expectation.