Origin of the Faraday effect in a transparent magnetic Mn2+glass

Abstract

The Faraday rotation (FR) in manganese aluminosilicate glass was measured at many light wavelengths in the visible and near-infrared spectral range and in a magnetic field up to 30 kOe. The authors also report magnetisation curves as a function of field and temperature in the same experimental conditions in order to analyse the origin of the FR. The magnetic field dependence of the FR exhibits an unusual non-monotonic behaviour at low temperatures. This is expected from the theoretical treatment since the Faraday rotation theta =AM+BH is linearly dependent on both the magnetisation and the applied magnetic field. At a given wavelength high- (295K) and low-temperature (1.4 and 4.2K) data may be analysed, in a first approximation, by only one set of A and B parameters. The theoretical treatment of the FR for magnetic systems having a quenched orbital momentum is reported. From the dependence of the FR on light frequency the authors experimentally separated three distinct contributions: the magnitude of the frequency-independent rotation due to microwave resonances agrees well with theoretical predictions, the two other contributions follow frequency laws entirely consistent with theoretical developments. The temperature dependence of the initial susceptibility was extracted from the FR measurements.