engleski

Irreversibility fields and pinning potentials in U/n treated Bi2223/Ag tapes

The magnetoresistance R(T, B) of virgin and four U-235 doped Bi2223/Ag tapes irradiated with thermal neutrons (U/n treated) has been measured in the temperature range T greater than or equal to 50 K and magnetic field B less than or equal to 1 T. For B greater than or equal to 20 mT the pinning potentials U-0 of U/n treated tapes were enhanced compared to that of virgin tape. The relative enhancement U-0(B, U/n)/U-0(8, virg.) increased with matching field B-phi and persisted to higher B at higher B-phi. For U/n treated samples, U-0 showed universal variation with B/B-phi : U-0(B less than or similar to B-phi) proportional to (B-phi/B)(proportional to) with alpha approximate to 0.5 and faster variation at higher B. The resistive irreversibility fields B-irr(T) of all U/n treated samples for T less than or similar to 100 K were also enhanced: B-irr (T, U/n)/B-irr (T, virg.) increased with B-phi and the enhancement persisted to lower T for higher B-phi. The maximum enhancements of B-irr scale well with the corresponding enhancements of U-0(B).

flux pinning; uranium doping; neutron irradiation

nije evidentirano