Search results for "Fluxon dynamics"

showing 3 items of 3 documents

Fluxon dynamics in Li–Al codoped MgB2 by microwave surface resistance measurements

2010

The magnetic-field-induced variations of the microwave surface resistance, Rs, have been investigated in ceramic Mg_(1-x)(LiAl)_xB_2, with x in the range 0.1 - 0.4. The measurements have been performed on increasing and decreasing the DC magnetic field, H0, at fixed temperatures. At low temperatures, we have observed a magnetic hysteresis in the Rs(H0) curves in all the investigated samples. On increasing the temperature, the range of H0 in which the hysteretic behavior is visible shrinks; however, in the sample with x=0.1 it is present up to temperatures close to Tc. We show that the field dependence of Rs can be quantitatively justified taking into account the critical-state effects on th…

MgB2 superconductorMicrowave surface resistanceMgB2 superconductor; Fluxon dynamics; Microwave surface resistanceFluxon dynamic
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Time evolution of the microwave second-order response of YBaCuO powder

2003

Transient effects in the microwave second-order response of YBaCuO powder are investigated. The time evolution of the second harmonic signal has been measured for about 300 s after the sample had been exposed to variations of the DC magnetic field. We show that in different time scales the transient response has different origin. In the time scale of milliseconds the transient response of samples in the critical state is ascribable to processes of flux redistribution induced by the switching on/off of the microwave field. At longer times, the time evolution of the second harmonic signal can be ascribed to motion of fluxons induced by the variation of the DC magnetic field. In particular, di…

SuperconductivityMillisecondMaterials scienceCondensed matter physicsFluxonCondensed Matter - SuperconductivityTime evolutionEnergy Engineering and Power TechnologySecond-harmonic generationFOS: Physical sciencesCondensed Matter PhysicsElectronic Optical and Magnetic MaterialsMagnetic fieldSuperconductivity (cond-mat.supr-con)Fluxon dynamics Magnetic relaxation Non-linear microwave responseTransient responseElectrical and Electronic EngineeringMicrowave
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Fluxon dynamics by microwave surface resistance measurements in MgB2

2003

Field-induced variations of the microwave surface resistance, Rs(H), have been investigated in high-density ceramic MgB2. At low temperatures, several peculiarities of the Rs(H) curves cannot be justified in the framework of models reported in the literature. We suggest that they are ascribable to the unconventional vortex structure in MgB2, related to the presence of two gaps. On the contrary, the results near Tc can be accounted for by the Coffey and Clem model, with fluxons moving in the flux-flow regime, provided that the anisotropy of the upper critical field is taken into due account.

SuperconductivityPhysicsFluxonCondensed matter physicsCondensed Matter - SuperconductivityFOS: Physical sciencesEnergy Engineering and Power TechnologyTourbillonMgB2 Microwave surface impedance Fluxon dynamicsCondensed Matter PhysicsMagnetic fluxElectronic Optical and Magnetic MaterialsVortexSuperconductivity (cond-mat.supr-con)Surface conductivityCondensed Matter::SuperconductivityElectrical and Electronic EngineeringAnisotropyCritical fieldPhysica C: Superconductivity
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