Anatoliy R. Prokopov

The paper deals with the magneto-optical eddy current method of flaw detection of conducting materials, in which epitaxial films of ferrite garnet are used as sensors. In particular, the possibilities of visualization of welded seams in magnetic and non-magnetic samples, as well as the defectoscopy of the seams themselves, are considered. The second part of the work is devoted to mathematical modeling of the distribution of the magnetic fields of eddy currents near similar defects.

Currently spin waves are considered for computation and data processing as an alternative to charge currents. Generation of spin waves by ultrashort laser pulses provides several important advances with respect to conventional approaches using microwaves. In particular, focused laser spot works as a point source for spin waves and allows for directional control of spin waves and switching between their different types. For further progress in this direction it is important to manipulate with the spectrum of the optically generated spin waves. Here we tackle this problem by launching spin waves by a sequence of femtosecond laser pulses with pulse interval much shorter than the relaxation time of the magnetization oscillations. This leads to the cumulative phenomenon and allows us to generate magnons in a specific narrow range of wavenumbers. The wavelength of spin waves can be tuned from 15 μm to hundreds of microns by sweeping the external magnetic field by only 10 Oe or by slight variation of the pulse repetition rate. Our findings expand the capabilities of the optical spin pump-probe technique and provide a new method for the spin wave generation and control.

We demonstrate application of integration scanning near-field optical microscopy and atomic force microscopy for investigation of magnetic and ferroelectric materials. This integration is made by using innovative optical and micromechanical components. Optical measuring head with cantilever holder was designed for both near-field optical microscopy and atomic force microscopy modes. Hollow pyramid cantilever with aperture at the tip was designed for registration both optical signal and tip=sample interaction forces. Cantilever aperture was made by ion beam at the center of pyramid. Same probe was used for both topography and domain structure visualization of magnetic samples. Bi: YIG-thin films topography and domain structure were investigated by this method as well as by conventional magnetic force microscopy (MFM). In integrated method of scanning nearfield polarization optical microscopy and atomic force microscopy samples were excited through cantilever aperture by tightly focused linearly polarized laser beam. Magneto-optical effect of the rotation of polarization plane of transmitted light depends on domain orientation. Visualization of magnetic domains was performed by detecting cross polarized component of transmitted light. Near field map of magnetic domains provides direct information of the magnetic moment of domains unlike MFM image which provides distribution of magnetic force gradient. Moreover, non-magnetic hollow-pyramid probe prevents sample from possible disturbances by internal magnetic moment of the MFM probe. Comparison of results obtained by near field polarization microscopy and conventional MFM was performed. We demonstrate possibility of investigation of topography and domain structure ferroelectric materials by integration method of near-field optical microscopy and atomic force microscopy.

A study of functioning of the magneto-optical method as part of magnetic force microscopy (MFM) is presented. Major errors in measuring the samples with MFM are discussed. The magneto-optical method enables us to perform a preliminary verification of a sample magnetic structure, providing minimal errors being specific for MFM. Design options for operation of the magneto-optical method as a part of MFM are proposed.

One-dimensional magnetophotonic microcavity crystals with nongarnet dielectric mirrors are created and investigated. The defect layers in the magnetophotonic crystals are represented by two...

The concept of vector magneto-optical magnetometry is proposed and experimentally demonstrated. The key element of the vector magnetometer is a transparent high Faraday activity magnetic film with a cubic crystal lattice. Magnetocrystalline anisotropy of the film leads to the three dimensional trajectory of the film magnetization when the magnetization is rotated by the control magnetic field. It makes the magnetization sensitive to all three components of the external magnetic field. This field can be found from the harmonic composition of the Faraday rotation dependence on the azimuth angle of the control magnetic field. The demonstrated vector magnetometer is promising for mapping and visualization of ultra small magnetic fields.

It is represented the results of modelling of magnetooptical properties in reflection polar geometry of one-dimensional photonic crystal, in which highly Bi-substituted iron garnet defect of composition Bi_1.0Y_0.5Gd_1.5Fe_4.2A_l0.8O₁₂ / Bi_2.8Y_0.2Fe₅Oi₂ is located between the dielectric Bragg mirrors (SiO₂ / TiO₂)^m (were m is number of layer pairs) and buffer SiO₂ and gold top layers of different thicknesses is placed on structure. The modification of spectral line- shapes of microcavity and Tamm plasmon-polariton modes depending on m is found.