This work is devoted to the experimental investigation of the magneto-optical properties of yttrium-iron garnet used as a sensitive element of a fiber-optical magnetic field sensor. The block diagram of the experimental stand and methods of measurement are described. The magneto-optical effect in some YIG samples with different thickness of epitaxial layer is studied, presence of a magneto-optical properties hysteresis is established and its value is measured. Design recommendations for the developed sensor are given.

Due to water molecules adsorption the reversible change of domains width and domain structure reconstruction in bismuth-doped ferrite-garnet thin films with perpendicular magnetic anisotropy was observed. The change of domains width was 15% in saturated water vapor at room temperature. The decrease of domains width is explained by the reduction of effective perpendicular magnetic anisotropy constant due to water molecules adsorption.

It has been found using the Faraday-effect magneto-optic method that the width of magnetic domains of the labyrinth domain structure in bismuth-containing iron garnet films with perpendicular anisotropy changes considerably after the adsorption of methanol molecules. A maximum change in domain width of 50% has been observed in methanol saturated vapor. This effect is reversible. A decrease in domain width under adsorption has been attributed to a decrease in the effective constant of the perpendicular magnetic anisotropy of the film caused by the adsorption of methanol molecules.

An efficient technology was developed for growing the gadolinium gallium garnet (GGG) single-crystal films doped with Nd 3+ or Cr and Ca ions. The films with thickness up to 100 µm have been grown by liquid-phase epitaxy method on undoped GGG substrates of small and big sizes (5–8 mm and up to 76 mm in diameter, respectively). The dependence of absorption, luminescence spectra and optical losses at the wavelength of 1 µm on growth temperature and melt-solution composition was studied. We demonstrated that Cr 4+ centers have been implemented in epitaxial films and these films may be used as passive Q-switches for laser systems.

Bi-substituted ferrite garnet (R Bi)(3)(M Fe)(5)O-12 epitaxial films with anomalously high (up to 1.2 deg/mum at RT) specific Faraday rotation provide an unique possibility of magneto-optical imaging of magnetic field microdistributions with a sub-micron resolution close to the diffraction limit. In the present work we give a detailed description of the physical principles and various applications of such films in materials science, microelectronics, magnetic testing and nondestructive evaluation (NDE) of defects in both ferromagnetic and non-ferrous metal components. In the latter case eddy-current excitation is used to reveal flaws, cracks and corrosion. The technique is ideal for not only detailed inspections, but also for rapid scanning over large areas to quickly determine structural condition of the part.

A method based on magnetooptical visualization of stray magnetic fields is proposed for determining the topogram of stray micromagnetic fields. Bismuth-substituted ferrite-garnet epitaxial films with easy-plane magnetic anisotropy are involved in the visualization procedure. The optimal magnetic parameters of these films are calculated as functions of the magnetic parameters of a medium under study and the linear parameters of magnetic microirregularities. Topograms of micromagnetic fields are obtained for certain magnetic-recording media.

Advantages of hysteresis-free ferrite-garnet magneto-optical films with the easy-plane magnetic anisotropy over uniaxial magnetic films in nondestructive testing of various magnetic materials and devices based on such materials are considered.

The potentialities provided by bismuth-containing garnet ferrite films with uniaxial anisotropy and easy-plane anisotropy for the visualization of spatially nonuniform magnetic fields in magnetooptic nondestructive testing are compared.

The advantages of magneto-optical ferrite-garnet films with a magnetic anisotropy of the "easy-plane" type over conventional uniaxial films used for visualization of magnetic scattering fields in various magnetic media are discussed. The spatial resolution in visualization of a digital record reaches 0.7 mum, and the dynamic range in visualization of an analog record exceeds 56 dB.

Results of nondestructive testing of “cracks” in standard steel samples using magneto-optical ferrite-garnet films with the easy-plane anisotropy are given.

The application of bismuth-substituted ferrite-garnet epitaxial structures for the spatial characterization of magnetic field distributions has been studied. These structures, consisting of a GGG substrate with BiLu(FeGa)5O12 film grown by the liquid phase epitaxy method, were supplied by an Al mirror, thus enabling a doubling of the Faraday effect. The structures have been successfully used for the visualization of magnetic fields of various origins, including magnetic cards, tapes, floppy and hard disks, and magnetic domain structures.