Dmitry A. Suslov

Composite tapes based on high-temperature superconductor (HTSC) films of the Y-Ba-Cu-O family can be used to create permanent superconducting magnets (PSM) that capture and maintain a constant magnetic field for a long time at temperatures of 90 K and below. In this paper, an original PSM design in the solenoid configuration consisting of rings of HTSC tapes is proposed. The results of a study of the process of capturing and holding magnetic fields in the solenoid are presented, including the dependence of the magnetic field in the solenoid center on the temperature after switching off the external field source, followed by cooling the PSM in the field. The stability of the held field in the PSM at a constant temperature is also considered. The experiments were carried out at temperatures from 3 to 100 K, in a magnetic field of up to 6.4 T. The possibility of using solenoids based on HTSC tapes for applications in promising solid-state cooling systems based on the magnetocaloric effect is discussed.

An algorithm for determining the magnetization of sub-lattices of a two-lattice ferrimagnet with a compensation point is proposed. To express the analytical dependence of magnetization on temperature, an approximation by the Brillouin function is explicitly used. A scheme for determining the magnetization of sub-lattices based on the use of temperature values of four characteristic points of the lower branch of the phase diagram is presented. A system of equations is obtained that relates the parameters of characteristic points with the values of magnetization at the initial point and at the maximum point of the diagram at a temperature above compensation. By solving the above system of equations, fairly simple analytical expressions are obtained that determine the saturation magnetization values of both sub-lattices through the parameters of characteristic points of the lower branch of the phase diagram. The proposed technique is applied to the determination of the magnetization of sub-lattices in experiments to measure the total magnetization performed on films of two different compositions using a vibrating magnetometer. To verify the obtained values, a comparison was performed with the data obtained in the experiment, which showed a good coincidence of the calculated data with the experimental ones.

For the purpose of studying the noncollinear phase in ferrimagnetic films with a magnetic compensation point, a technique has been developed and an experimental setup has been fabricated for observing phase transitions in ferrimagnetic films using magneto-optical contrast. The unique feature of the setup with a superconducting magnet is the presence of a controllable lateral temperature gradient that allows simultaneous observation of various phase states in ferrimagnetic films in the range of magnetic fields and temperatures using the magneto-optical method. Using the developed setup, zones of different magnetic ordering were observed for rare earth garnet ferrites in the range of magnetic fields from 0 to 10 T and temperatures from 150 to 400 K. The lateral temperature gradient in the film plane could be varied from 0 to 12 K. Different phases of the first-order spin-reorientation transition were observed in films with a composition of (BiYGd)₃(FeGa)₅O₁₂ using this technique.

The experimental discovery of the suppression effect of the non-collinear phase in strong magnetic fields near the compensation point in ferrimagnetic structures was made. The observations were carried out using the magneto-optical method by creating a lateral temperature gradient in the plane of the epitaxial films of iron garnets. The non-collinear phase is absent in weak magnetic fields. If an external magnetic field exceeds the first critical value, the non-collinear phase arises near the compensation point. The temperature range of the non-collinear phase expands due to the field increase up to the second critical value. Further field increases conversely reduce the temperature range of the non-collinear phase so that the field above the second critical value causes the disappearance of the non-collinear phase. The effect of the occurrence and suppression of the non-collinear phase is demonstrated on samples of two types of iron garnet films with two and three magnetic sublattices. Phase diagrams of the magnetic states in the vicinity of the critical point are constructed, and it is shown that the region of existence of the non-collinear phase in a two-sublattice magnet is smaller than in a three-sublattice one.

A method for the magneto-optical visualization of magnetic phases in ferrimagnets in the vicinity of the compensation point in the lateral temperature gradient is described. On the example of films of bismuth–gadolinium ferrite garnet, zones corresponding to collinear and non-collinear magnetic phases were observed, depending on the temperature and the magnitude of the magnetic field in the range from 0 to 10 T.

Study and implementation of innovative systems of environmentally friendly and energy-efficient transport based on magnetic levitation, the principle of operation of which is based on the use of new solid-state magnetic materials based on compounds of rare earth materials, in particular materials with high-temperature superconductivity based on Y, permanent magnets based on Nd and Sm and magnetocaloric alloys based on Dy, Tb are of great interest throughout the world. In this work, the basic principles of magneto-levitation transport with the most economical principle of acceleration and deceleration - gravitational - are studied experimentally on mock-ups. The strength characteristics were measured: the levitation force and the lateral stabilization force, as well as losses during periodic translational motion of a cryostat with high-temperature superconducting elements made of ceramic material Y-Ba-Cu-O over the paths of permanent magnets made of the rare-earth compound Nd-Fe-B. A system for measuring the speed and compensation of losses for the implementation of continuous motion has been created and tested. The presented results indicate the possibility of scaling the layout project. It is concluded that the investigated scheme may be of practical interest for intracity and local transport communication with high comfort, environmental friendliness and record economy in the case of a successful solution of the problem of cooling HTSC elements to the temperature of the phase transition to the superconducting state, for example, using new principles of solid-state magnetic cooling based on compounds Dy-N, Tb-Ni, etc.

New economy - an innovative economy - forms new challenges and new solutions in all spheres of human activity. A key feature of the new economic ties is their global nature. Transport systems based on existing technologies cannot provide the necessary growth of new economic ties and the effective provision of the existing business. New transport systems based on new technologies for transporting goods and passengers in compliance with the principles of energy and financial efficiency, as well as environmental safety, create the foundation for sustainable development of countries and regions, including improving the quality of life of the population and human potential. The rapid speed economic is been formed for nowadays commercial transportation communication. And a realization of any transport project has always tight connection and mutually conditioned with another project type energetics. So, the problem of energy efficiency and energy supply becomes a key factor of a choice of the most energy efficiency of a base system in any transport complex! Aim: The purpose of this article is to provide an alternative solution - the Integrated transit transport system (ITTS) of the Russian Federation based on the energy save technologies of Vacuum magnetic levitation transport (VMLT). Methods: The article discusses organizational, technical, energy efficient, logistic and economic solutions in the field of high-speed land corridors and "energy pipelines" projects, created on the basis of the latest vacuum magnetic levitation transport (VMLT) technologies. Experimental stands used are described, an overview of practical results obtained in laboratory and production equipment, and preliminary results of VMLT prototypings based on a miniature route of rare-earth magnets and leviters based on ceramics from a high-temperature superconductor, possibilities, prospects and the first experimental results of development are presented. of the main critical elements of the WMLT technology. The paper describes the results of using modern additive manufacturing technologies (3d printing) to create a system model, microcryogenic systems, HTSC and REM "nitrogen" temperature levels to create trace elements and system models, with the ability to scale to the current full-size model of the next generation. Results: The presented calculations show the practical possibility of further development and implementation of this project, as well as its very high effectiveness compared to existing systems in terms of practical application, economic, manufacturing, energy efficiency and environmental safety.

The Russian Federation is located at the crossroads of the trade routes of the Eurasian continent, where a significant volume of the transport flow of the world’s trade is formed. The transport potential of the territory of Russia, when implemented as an Integral Transit Transport System (ITTS), is comparable to the benefits from the traditional export of hydrocarbons and other raw materials. Analyzing the efficiency of transport systems, the key is the energy approach. The concept of ITTS is considered, based on all known and being developed transport lines, including high-speed vacuum magnetic levitation transport (VMLT). The fundamental problems are discussed being on the way to achieving the maximal speed, energy efficiency and throughput of VMLT. The preliminary findings are presented obtained from experiments on the test model of the VMLT route. It is concluded that there is a need for a deeper study of the properties of magnetic and superconducting materials in extreme high fields, power and speed regimes to search for fundamentally new technical solutions for the creation of VMLT