Magneto-optical effects in ferrite garnet thin-film structures and single-crystalline substrates

The Faraday and Kerr magneto-optical effects in thin-film structures based on the yttrium iron garnet Y3Fe5O12 and bismuth-substituted yttrium iron garnet BiY2Fe5O12, with layer thicknesses not exceeding several tens of nanometers, as well as in the dielectric substrates including Gd3Ga5O12, Nd3Ga5O12, Y3Al5O12, and Al2O3 are analyzed and discussed. The dispersion of the Verdet constant and the polar Kerr polar effect are examined for bare substrates. The contributions of weakly magnetic substrates of different compositions to the overall magneto-optical response of thin-film/substrate structures are analyzed in detail, along with the Faraday and Kerr rotation spectra of the films grown on these substrates. Interface effects are also investigated, particularly those arising from elemental interdiffusion and a high density of misfit dislocations at the film–substrate boundary. These phenomena lead to the formation of magnetic inhomogeneities and critical (relaxed) layers in ultrathin films. It is shown that, in the presence of such inhomogeneities, reduction of film thickness results in a significant suppression of the magneto-optical effects. This degradation is most pronounced in structures fabricated on the Al2O3 substrates.