H-T Phase Diagram of Rare-Earth -- Transition Metal Alloy in the Vicinity of the Compensation Point

Anomalous hysteresis loops of ferrimagnetic amorphous alloys in high magnetic field and in the vicinity of the compensation temperature have so far been explained by sample inhomogeneities. We obtain H-T magnetic phase diagram for ferrimagnetic GdFeCo alloy using a two-sublattice model in the paramagnetic rare-earth ion approximation and taking into account rare-earth (Gd) magnetic anisotropy. It is shown that if the magnetic anisotropy of the $f$-sublattice is larger than that of the $d$-sublattice, the tricritical point can be at higher temperature than the compensation point. The obtained phase diagram explains the observed anomalous hysteresis loops as a result of high-field magnetic phase transition, the order of which changes with temperature. It also implies that in the vicinity of the magnetic compensation point the shape of magnetic hysteresis loop is strongly temperature dependent.Comment: 8 pages, 3 figure

Selection Rules for All-Optical Magnetic Recording in Iron Garnet

Finding an electronic transition a subtle excitation of which can launch dramatic changes of electric, optical or magnetic properties of media is one of the long-standing dreams in the field of photo-induced phase transitions [1-5]. Therefore the discovery of the magnetization switching only by a femtosecond laser pulse [6-10] triggered intense discussions about mechanisms responsible for these laser-induced changes. Here we report the experimentally revealed selection rules on polarization and wavelengths of ultrafast photo-magnetic recording in Co-doped garnet film and identify the workspace of the parameters (magnetic damping, wavelength and polarization of light) allowing this effect. The all-optical magnetic switching under both single pulse and multiple-pulse sequences can be achieved at room temperature, in narrow spectral ranges with light polarized either along or crystallographic axes of the garnet. The revealed selection rules indicate that the excitations responsible for the coupling of light to spins are d-electron transitions in octahedral and tetrahedral Co-sublattices, respectively

Fast recognition of marine particles in underwater digital holography

The issue of fast recognition of marine particles in situ by digital holography methods is considered. An algorithm for the classification of marine particles by morphological features is proposed. Preliminary results and estimation of accuracy of the proposed algorithm are presented

Educational research networks principles of organization

Relevance. Modern society has global transformations; as a result, the level characteristics of its system development are changing, new opportunities and new situations to implement a self-organizing system to solve problems of self-government appear. Thus, there is the need to organize the multiplicity of interactions in the new environment, including education. The success of the development mechanisms, organizing innovative activities in the educational systems of different levels is largely determined by the active development of interaction network forms and interaction effective management. The article is devoted to development of theoretical ideas about the processes of network interaction in education to justify and describe the principles of modern scientific-educational network on the basis of system-synergetic approach. A leading approach to study this problem can be considered as system-synergetic which allows studying network interaction within the scientific and educational network as a holistic entity consisting of interrelated elements, structured and complex. The results of the study showed that described principles of effective networking and the conditions of scientific and educational networks development allow you to combine and re-combine the accumulated actors of this knowledge and practical experience interaction, turning them into the means of its innovative activities. The article can be useful to heads of educational institutions of different levels, as well as researchers of innovative processes development problems in education. © 2018 Authors

Digital holographic camera for plankton monitoring

A submersible digital holographic camera for measuring plankton and other particles is described. The camera provides underwater recording of digital holograms of water volume containing plankton followed by automatic restoration of holographic images of plankton species, determination of their sizes, shapes, and concentrations, and their recognition and classification. Particles with sizes of 200 μm and larger are analyzed. The water volume registered per exposure is about 1 L. The special features of the software for automatic information retrieval from digital holograms are discussed. Examples of application of the camera as an integral part of the hardware-software complex for field measurements are given. Prospects for application of this complex for ecological monitoring are discussed. The recognition criterion of the digital holographic camera and the data volume and the averaging time required for obtaining statistically reliable data on plankton species are also given

High Field Anomalies of Equilibrium and Ultrafast Magnetism in Rare-Earth-Transition Metal Ferrimagnets

Magneto-optical spectroscopy in fields up to 30 Tesla reveals anomalies in the equilibrium and ultrafast magnetic properties of the ferrimagnetic rare-earth-transition metal alloy TbFeCo. In particular, in the vicinity of the magnetization compensation temperature, each of the magnetizations of the antiferromagnetically coupled Tb and FeCo sublattices show triple hysteresis loops. Contrary to state-of-the-art theory, which explains such loops by sample inhomogeneities, here we show that they are an intrinsic property of the rare-earth ferrimagnets. Assuming that the rare-earth ions are paramagnetic and have a non-zero orbital momentum in the ground state and, therefore, a large magnetic anisotropy, we are able to reproduce the experimentally observed behavior in equilibrium. The same theory is also able to describe the experimentally observed critical slowdown of the spin dynamics in the vicinity of the magnetization compensation temperature, emphasizing the role played by the orbital momentum in static and ultrafast magnetism of ferrimagnets

Effect of frictional treatment on the microstructure and surface properties of low-carbon steel

The microstructure of annealed low-carbon (0.17 wt% C) steel subjected to frictional treatment with a sliding hard-alloy indenter is studied by EBSD analysis, as well as its micromechanical characteristics. It has been found that frictional treatment results in high dispersity of the structure in the steel surface, down to the submicro- and nanocrystalline state. Instrumented microindentation has revealed that, under all the loads, the values of the contact elastic modulus E ∗ of low-carbon (0.17 wt% C) steel after frictional treatment are lower than those in the initial annealed state. Particularly, the mean value of E ∗ decreases from 208 to 168 GPa under a load of 1 gf on the indenter, from 213 to 176 GPa under a load of 25 gf and from 204 to 155 GPa under a load of 200 gf. It is for the first time that the effect of a decrease in the elastic modulus is observed for a carbon steel subjected to frictional treatment. It also follows from the microindentation data that frictional treatment increases the capability of the surface of annealed low-carbon (0.17 wt% C) steel to withstand higher contact loads prior to plastic deformation. © 2018 Author(s)

CYTOMETRIC ANALYSIS OF THE SPECTRUM SUBPOPULATION OF T LYMPHOCYTES IN THE EARLY FORMS OF CHRONIC BRAIN ISCHEMIA VETERANS OF MODERN WARS

Formation of the earliest forms of chronic brain ischemia veterans of modern wars accompanied by an increase in the systemic circulation of the population of T lymphocytes and monocytes, reflecting the activation of central mechanisms lymphopoiesis. In step vascular encephalopathy is an increase in circulating pool of T lymphocytes expressing the activation markers early positive reflecting readiness cells to IL-2 dependent proliferation. When progessirovanii chronic brain ischemia decreased levels of circulating T-regulatory cells, which may reflect a violation of self-tolerance in relation to brain antigens