Seminarium Międzynarodowego Laboratorium Silnych Pól Magnetycznych i Niskich Temperatur PAN
ul. Gajowicka 95, sala seminaryjna (nowy budynek, II piętro)
Developement of the original techniques for direct study of the magnetocaloric effect in strong magnetic fields in prospective magnetic materials
V. Koledov and E. T. Dilmieva
Kotelnikov IRE RAS, Moscow
Currently there is an exponentially growing number of papers published all around the world on the study of magnetocaloric effect (MCE) in solids with magnetic and magnetostructural phase transitions (PTs) near room temperature. These papers, reveal mostly interest in synthesis and characterization of the new materials and in fundamental study of the problem of energy exchange among subsystems of solids near PTs under sufficiently strong magnetic fields. Controversially there only a few publications on design and experimental test of the prototypes of the magnetocaloric thermodynamical devices, such as heat pumps or refrigerators. To our opinion the mane obstacle on the way towards the design of working prototype of the commercial devices is the lack of reliable experimental data on the functional properties of the prospective magnetocaloric materials. The crucial of these properties are: adiabatic temperature change (ΔT), isothermal specific heat transfer (ΔQ), magnetic field work on reversal magnetization near critical point of magnetic or magnetostructural PTs ( W= ∫Hdm) and relaxation time t of structural, magnetic and thermodynamical processes at PT. We suggest the set of the original complementary experimental techniques which are to fill the gap in the knowledge of the functional properties of materials with MCE. We discuss the first results of the tests of the techniques, which include direct ΔQ, ΔT, W measurement techniques, dilatometer for magnetic shape memory and optical microscope for direct martensitic twins motion study in high magnetic field of Bitter magnet up to 14 T. The particular attention is paid to possibility of the development of the new techniques for the direct measuring of MCE in strong pulsed magnetic fields.
