Real and apparent loss suppression in MgB2 superconducting composites

Rauh²,

J. Phys.: Condens. Matter

2005

The Bean-Livingston barrier at the interface of type-II superconductor/soft-magnet heterostructures is studied on the basis of the classical London approach. This shows a characteristic dependence on the geometry of the particular structure and its interface as well as on the relative permeability of the involved magnetic constituent. The modification of the barrier by the presence of the magnet can be significant, as demonstrated for a cylindrical superconducting filament covered with a coaxial magnetic sheath. Using typical values of the relative permeability, the critical field of first penetration of magnetic flux is predicted to be strongly enhanced, whereas the variation of the average critical current density with the external field is strongly depressed, in accord with the observations of recent experiments.

Section: B Finite Curved Geometrysupporting

confidence: 82%

The Bean–Livingston barrier at a superconductor/magnet interface

Rauh²,

J. Phys.: Condens. Matter

2005

“…Notice also, that the above studied modification of the Bean-Livingston barrier is not reduced to the shielding effect of the magnetic sheath solely 25,36,37,38 because the latter does not account for the magnetic flux expelling from the filament itself. For example, in the limit R 1 ≫ λ, d the maximum field on the superconductor surface amounts to H max = 2H 0 /(1 + µd/R 1 ) while for the shielding of the normal core it is H max = H 0 /(1 + µd/2R 1 ) (see Ref.…”

Section: Discussionmentioning

confidence: 92%

“…31,32 As was observed in recent experiments, such structures exhibit enhanced superconducting critical currents over a wide range of external magnetic field 31,[33][34][35] as well as a strong reduction of ac losses in the external field. [36][37][38] At the same time, a theoretical description of the influence of soft-magnet shielding on the current-carrying properties of type-II superconductor filaments is still lacking.…”

Section: Introductionmentioning

confidence: 99%

Entry of magnetic flux into a magnetically shielded type-II superconductor filament

2005

Phys. Rev. B

In the framework of the London approximation the magnetic flux penetration into a type-II superconductor filament surrounded by a soft-magnet sheath and exposed to a transverse external magnetic field is studied. The lower transverse critical field as well as the critical field and the critical current of the first vortex nucleation at the superconductor/magnet interface are calculated on the basis of an exact solution for a vortex of arbitrary plane configuration. The Bean-Livingston barrier against the vortex nucleation is shown to strongly depend on the magnet sheath parameters.

“…1. To facilitate further considerations, we refer to an assumption invoked in previous works 9,10 , viz. that the total magnetic induction in the SC core can be decomposed according to…”

Section: Resultsmentioning

confidence: 99%

The Bean model of the critical state in a magnetically shielded superconductor filament

Rauh

et al. 2006

J. Phys.: Conf. Ser.

We study the magnetization of a cylindrical type-II superconductor filament covered by a coaxial soft-magnet sheath and exposed to an applied transverse magnetic field. Examining penetration of magnetic flux into the superconductor core of the filament on the basis of the Bean model of the critical state, we find that the presence of a non-hysteretic magnetic sheath can strongly enhance the field of full penetration of magnetic flux. The average magnetization of the superconductor/magnet heterostructure under consideration and hysteresis AC losses in the core of the filament are calculated as well.