Flux Jumps and H-T Diagram of Instability for MgB2 |
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Authors: | Victor Chabanenko Roman Puźniak Adam Nabiałek Sergei Vasiliev Vladimir Rusakov Loh Huanqian Ritta Szymczak Henryk Szymczak Jan Jun Janusz Karpiński Vitaly Finkel |
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Affiliation: | (1) Physico-Technical Institute NAS, 72 R. Luxemburg str., 83114 Donetsk, Ukraine;(2) Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland;(3) Donetsk National University, 24 Universitetskaja str., 83055 Donetsk, Ukraine;(4) Solid State Physics Laboratory ETH, 8093-Zürich, Switzerland;(5) National Science Center Kharkov Institute of Physics and Technology, 1st Academicheskaya St., 61108 Kharkov, Ukraine |
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Abstract: | We present a study of magneto-thermal instabilities in polycrystalline MgB2 superconductor, by magnetic hysteresis loop measurements and by investigations of magnetic flux dynamics with a miniature Hall probe. Temperature and magnetic field ranges where the flux jumps may be observed have been determined. On the basis of measurements of the magnetic flux dynamics, an average magnetic diffusivity describing the process of the flux jump is estimated. This parameter is compared with the thermal and magnetic diffusivities calculated on the basis of available data for thermal conductivity, heat capacity and resistivity. It is shown that the estimated value of the field of the first flux jump is influenced significantly by the field dependence of specific heat. In order to explain the observed phenomenon, the temperature reached by the sample during the flux jump at different magnetic fields is calculated. |
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