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Registration Number

0220U000702, 0120U000267 , R & D reports

Title

Nano-hetero-structures on the base of magnetic half-metals and superconductors as promising functional materials for superconducting spintronics: electrical, magnetic and optical properties, effects of electronics topological state

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Head

Kryvoruchko Volodymyr Mykolayovych, Доктор фізико-математичних наук

Registration Date

14-12-2020

Organization

A.A. Galkin Physics and Engineering Institute of National Academy of Science of the Ukraine

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The goals of the work - experimental research and theoretical calculations of physical properties of perspective nano-hetero-materials and establishment of scientifically substantiated principles of novel functional materials for spin electronics. Objects of research - superconductor - half-metal ferromagnet nanocomposites, crystalline and amorphous nickel films, hybrid nano-heterostructures based on superconductors and magnets. Research methods - Andreev spectroscopy; measurement of transport/resistive properties of nanocomposites; magnetic, magneto-optical, transport and optical measurements, electron microscopy studies; variations of density and volume concentration of components; theoretical modeling of transport properties of nanoscale hybrid structures based on superconductors and magnets. The transition to a superconducting state of nanocomposites from microparticles of the Bi2Sr2Ca2Cu3O6 superconductor with a d-symmetry of the order parameter (Bi2223) and nanoparticles of the magnet La2/3Sr1/3MnO3 (LSMO) - Bi2223: LSMO nanocomposites has been investigated. It is established that experimental dependences of the resistive superconducting transition and current-voltage characteristics of superconducting bulk nanocomposite samples, with the content of Bi2223: LSMO components (4: 1), are well described by the Berezinsky - Kosterlitz - Thouless model for two-dimensional superconductors. The observed transport features are due to the current flow along the ferromagnetic nanogranules LSMO, which cover Bi2223 microgranules. The influence of Ni film structure on the degree of the spin polarization of conduction electrons, as well as on other physical (mainly magnetic) properties that are essential for spin electronics, has been established. It was found that annealing of amorphous Ni films at temperatures (Tann = 300 - 350 C) causes their crystallization with the formation of FCC phase, restores their magnetic, optical, magneto-optical, and transport properties, that are typical for massive crystalline nickel. Using existing technology, Heusler alloys have been prepared for further detailed study of their electronic structure and physical properties. Single-phase Fe2CrGa alloy suitable for further study of its physical characteristics was obtained. Two- or multiphase Co2ZrGe and Co2HfGe alloys were considered unsuitable for further experimental research. Their fabrication requires improvement of the existing technology. Conductivity and current fluctuations in layered hybrid structures formed by a metal injector, nanosized insulator, normal metal layer and a superconductor have been studied. It is shown that the measurements of the shot noise and differential conductivity in such samples can serve as a source of reliable information about the presence of two energy bands with different superconducting gaps.

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Дмитренко В.Ю.
Житлухіна О.С.
Кудрявцев Ю.В.
Таренков В.Ю.
Уваров М.В.