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Mössbauer studies of systems that include nanoparticles of Fe compounds and alloys – nanocomposites of SiO2 type lattice with embedded particles of various crystallographic modifications of Fe2O3 or spinel structure ferrites MFe2O4 (where M = Co, Ni, Zn, Cd, Cu, and Mn). Nanogranullar systems prepared by controlled crystallization of amorphous (i.e., metastable) Fe compounds produced by fast cooling processes.
Flow properties of superfluid He II (stability of oscillating boundary layer flow) and quantum turbulence (temporal decay of counterflow turbulence) above 1.3 K are studied using second sound attenuation technique. Flows of rotating superfluid 3He phases and of He II in zero temperature limit are investigated in collaboration with Finland and UK. Experiments on high Rayleigh number cryogenic thermal convection are under preparation.
We study magnetism and magneto-elasticity of rare-earth and uranium intermetallic compounds with high content of 3d-metal (Fe and Co). They combine the localized magnetism of the f-electron sublattice with the itinerant magnetism of the 3d-sublattice and belong to an important class of modern magnetic materials. The work is usually performed on high-quality single crystals grown in our lab. Some particular results are: Celý text >>
Research of magnetic properties of superconductors by means of SQUID magnetometers. The aim of our work is to understand magnetic properties of superconductors in the low-field region of the H-T phase diagram. These properties are studied from the temperature dependences of dc magnetization, ac susceptibility, M-H measurements and relaxation processes.
Research of relaxation processes in magnetic materials and systems of vortices in various forms (thin layers, single crystals, tapes, ceramics) of high-temperature superconductors. Experimental observation of magnitude and stability of induced currents in a broad range of external conditions (temperature, magnitude and orientation of the magnetic field). Model description of these phenomena.
Celý text >>The group is involved in preparation and study of magnetic materials, mainly of the magnetic ones, with very fine (amorphous or nanometric) atomic structure. Magnetic, magneto-elastic and magneto-transport properties are investigated. The aim of the reasearch is clarification of microphysical mechanisms of the properties, but also their application for practical purposes.
Celý text >>Construction of general response theory of nonlinear nonequilibrium systems, which is based on decomposition of system response operators. Study of magnetization processes and their dependence on microstructure and external conditions (stress, temperature). Development of the method of nondestructive testing of magnetic materials.
Celý text >>Investigation of magnetic properties of surfaces and interfaces of thin layers, multilayers and layered structures with stress at the origin and microphysical properties of surface and bulk excitations, interlayer exchange interactions and anisotropic energy of interfaces. Primary experimental technique - low-energy spin spectroscopy (ferromagnetic resonance) and topographic spin-electron resonance.
Celý text >>The extensive study of the magnetic systems appropriate for use in medicine, in particular for the magnetic hyperthermia, has been devoted especially to nanoparticles of CoFe2O4. Annealing of the nanoparticle powder at temperatures of 400-800 °C resulted in the average particle size of 18 to 40 nm. By Mössbauer spectroscopy of the 57Fe isotope enabled to determine the distribution of Fe ions between tetrahedral and octahedral positions. Based on these data the inversion degree of the spinel lattice was determined. Celý text >>
The thermally activated quantum turbulence in He II has been studied, in a canal with superfluid holes not allowing the normal component of a finite viscosity to flow through. Thus, the turbulence in the canal was generated by a longitudinal flow of the pure superfluid component. Besides the already in literature described stationary state of the flow, we discovered a new turbulent state in which the density of quantum vortices is proportional to the transport superfluid velocity, with a parabolic velocity profile like in a classical viscous liquid flow. Celý text >>
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