V. V. Randoshkin

Nondestructive testing with the help of hysteresis-free magneto-optical films

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.

Luminescence of gadolinium garnet single crystals excited by synchrotron radiation

Single crystals of gadolinium-containing garnets with the compositions Gd3Ga5O12, Gd3(Sc,Ga)5O12:Cr, and (Gd,Ca)3(Mg,Zr,Ga)5O12 were grown using the Czochralski technique, and their luminescence was studied under the conditions of excitation with “white” synchrotron radiation. The observed differences in the luminescence spectra are discussed.

Advantages of anhysteretic magnetooptic films in nondestructive testing

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.

Effect of Gd2O3 concentration in Bi-containing high-temperature solutions on the luminescence of epitaxial Gd3Ga5O12 films

Single-crystal gadolinium gallium garnet films have been grown by liquid-phase epitaxy on (111) Gd3Ga5O12 substrates from supercooled Bi2O3-B2O3 fluxed melts at different Gd2O3 concentrations. The luminescence spectra of the films have been measured at 10 and 300 K under unmonochromatized synchrotron X-ray excitation and selective UV synchrotron excitation. The Bi3+ luminescence is discussed.

Spectral and luminescence properties of gadolinium gallium garnet epitaxial films doped with terbium

Gadolinium gallium garnet single-crystal films containing terbium are grown through liquid-phase epitaxy from a supercooled solution melt in the PbO-B2O3 system. The optical absorption spectra in the wavelength range 0.2–10.0 μm and the luminescence spectra excited by synchrotron radiation with energies in the range 3.5–30.0 eV are investigated at temperatures of 10 and 300 K. It is revealed that the optical absorption spectra contain an absorption band with the maximum at a wavelength λ ≈0.260 μm, which corresponds to the spin-allowed electric dipole transition between the electronic configurations 4f8(7F6) → 4f7(8S)5d of the Tb3+ ions. The narrow low-intensity absorption bands attributed to the 4f → 4f transitions from the 7F6 ground level to the 7F0–5 multiplet levels of the Tb3+ ions are observed in the wavelength range 1.7–10.0 μm. In the luminescence spectra measured at a temperature of 10 K, the highest intensity is observed for a band with the maximum at a wavelength λ ≈ 0.544 μm, which is associated with the 5D4 → 7F5 radiative transition in the Tb3+ ion.

Classical dependence of the domain wall velocity on the magnetic field in garnet ferrite films with orthorhombic magnetic anisotropy

The dependence of the domain wall velocity V on the acting magnetic field H is investigated for bismuth-containing single-crystal garnet ferrite films with orthorhombic magnetic anisotropy. It is shown that this dependence includes both the initial linear portion and a saturation portion and exhibits a complex behavior. This behavior is explained within the model of domain wall motion with spin wave radiation.

Visualization of “cracks” in steel using ferrite-garnet magneto-optical films with easy-plane anisotropy

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

Luminescence of gadolinium gallium garnet epitaxial films under excitation by synchrotron radiation

The luminescence excited by synchrotron radiation in gadolinium gallium garnet single-crystal films grown by liquid-phase epitaxy from lead-and bismuth-containing solution melts on Gd3Ga5O12 substrates is investigated. It is shown that the luminescence intensity in the visible range of the spectrum depends on the type and concentration of impurity ions passing from the solvent into the film.

Domain dynamics in (210)-oriented single-crystal (Bi,Y,Lu,Pr)3(Fe,Ga)5O12 films

Using high-speed photography, dynamic magnetic structures are studied in Bi-containing (210)-oriented single-crystal films of (Bi,Y,Lu,Pr)3(Fe,Ga)5O12 grown through liquid-phase epitaxy from an overcooled solution in the melt on (Gd,Ga)3(Mg,Zr,Ga)5O12 substrates. At various temperatures, the ranges of pulsed magnetic fields are determined in which unidirectional anisotropy of domain wall velocity and spatial distortions of moving domain walls are observed.

On the local magnetization reversal in front of a domain wall moving in a garnet ferrite film with orthorhombic magnetic anisotropy

The experimentally observed shapes of dynamic domains in garnet ferrite single-crystal films with (110) and (210) orientations are explained in terms of in-plane magnetic anisotropy of these films.