In a type-II superconductor the pinning properties and, in particular, the current dependence of the thermal activation energy U(J) determine the shape of the current-voltage (I-V) curve. The generation of higher harmonics in the magnetic response to an alternating magnetic field is a consequence of the non-linearity in the I-V characteristic. In this work we report our analysis of fundamental (?1) and third (?3) harmonics of the ac magnetic susceptibility on MgB2 bulk superconductors. In particular, measurements have been performed as a function of the temperature and the dc magnetic field, up to 9 T, for various frequencies and amplitudes of the ac magnetic field. By comparing the experimental susceptibility curves with numerical simulations of the magnetic diffusion in a type-II superconductor, we show that the frequency dependence of the third harmonic response can provide clear information about the characteristics of the non-linearity in the I-V curve and, therefore, the dynamical regimes governing the vortex motion in the analyzed samples.

Non-linear magnetic response of MgB2 bulk superconductors

M Polichetti;S Pace
2004

Abstract

In a type-II superconductor the pinning properties and, in particular, the current dependence of the thermal activation energy U(J) determine the shape of the current-voltage (I-V) curve. The generation of higher harmonics in the magnetic response to an alternating magnetic field is a consequence of the non-linearity in the I-V characteristic. In this work we report our analysis of fundamental (?1) and third (?3) harmonics of the ac magnetic susceptibility on MgB2 bulk superconductors. In particular, measurements have been performed as a function of the temperature and the dc magnetic field, up to 9 T, for various frequencies and amplitudes of the ac magnetic field. By comparing the experimental susceptibility curves with numerical simulations of the magnetic diffusion in a type-II superconductor, we show that the frequency dependence of the third harmonic response can provide clear information about the characteristics of the non-linearity in the I-V curve and, therefore, the dynamical regimes governing the vortex motion in the analyzed samples.
2004
Istituto Superconduttori, materiali innovativi e dispositivi - SPIN
Ac susceptibility
MgB2
Vortex dynamic
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/158461
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus ND
  • ???jsp.display-item.citation.isi??? ND
social impact