Retardation of the Magnetic Relaxation in High-Temperature Superconductors Near a Ferromagnet
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The creep of a magnetic flux trapped in a bulk high-temperature superconductor has been studied. It has been found that the magnetic relaxation is retarded when the superconductor is placed near a ferromagnet. The value of the retardation effect depends on the sequence of magnetization and the approach of the superconductor to a ferromagnet. The magnetic relaxation is fully suppressed when a superconducting sample first is magnetized and then is brought close to a ferromagnet. An interpretation of this effect has been discussed. Being magnetized, a ferromagnet produces its own magnetic field. While penetrating into a disk sample through its planes, the ferromagnet field induces screening currents, which circulate oppositely to the current that arises upon trapping of the magnetic flux. As a result, the stability of the magnetic structure is sharply improved since opposite driving forces can act on different sections of the vortices.
KeywordsHigh-Tc superconductors Trapped flux Magnetic relaxation
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- 5.Smolyak, B.M., Perelshtein, G.N., Ermakov, G.V., Postrekhin, E.V.: Physica C 341–348, 1129 (2000) Google Scholar