Oxide glasses with magnetic nanoparticles: transparent magnets(Faraday rotation and electron magnetic resonance studies)

摘要

In the first part of this paper we outline the state of the artin the field of magnetic nanoparticles in oxide glasses. Wedescribe the theoretical background of two complementarytechniques used for the studies of the state of paramagnetic ions,clusters and magnetic particles in a diamagnetic matrix, viz.,magnetooptical Faraday rotation (FR) and electron magneticresonance (EMR) and we overview previous results obtainedwith these techniques for several glass systems. In thesecond part, we highlight the case of potassium-alumina-borateglasses – a glassy system where doping with paramagneticoxides results in formation of magnetic particles at very lowcontents of paramagnetic additions: Fe_2O_3and MnO. In thespecial case when the ratio of the iron and manganese oxides in the charge is 3/2, magnetic nanoparticles with characteristicsclose to those of manganese ferrite are formed already at thefirst stage of the glass preparation. After thermal treatment allglasses show FR and EMR spectra attesting to the presenceof superparamagnetic nanoparticles, characterized by relativelybroad size and shape distributions. The formation of magneticnanoparticles confers to these glasses magnetic and magneto-optical properties typical of magnetically ordered substances.At the same time, the glasses remain transparent in a partof the visible and near infrared spectral range and displaya high FR value. Such properties make them particularlyinteresting for use as new media for various magneto-opticaldevices.