SPEROMAGNETISM IN HOMOGENEOUS OXIDE GLASSES CONTAINING A LARGE AMOUNT OF Fe^<3+> IONS

概要

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Structural and magnetic properties of homogeneous oxide glasses containing a large amount of Fe^<3+> ions, are reviewed. A comparative study of the glass and its corresponding crystal, mostly by Mossbauer spectroscopy, reveals that short-range atomic arrangements in the glass do not show much difference from that of the crystal, as far as a few interatomic distances are concerned. The magnetic state in the glasses is characterized by a narrow distribution and a Brillouin-function-like temperature dependence of the internal field, a rather sharply defined magnetic ordering temperature, and remarkable thermoremanence induced in the field-cooling experiments. Surprisingly large reduction in the magnetic ordering temperature of the glass is to be noted, when compared with the coresponding crystal. These observations are consistently interpreted by the concept of spero-magnetism proposed by Coey, where short-range antiferromagnetic order prevails only for a few atomic distances. It is pointed out that the Fe^<3+> ion is particularly favorable species as a network former in the homogeneous glasses because of its (3d)^5 configuration, being insensitive to crystal field effect.