Superconducting properties of the heavy-ions and neutron irradiated (Cu,C)Ba 2Ca n−1 Cu nO 2 n+4− δ ( n=3, 4 and 5)

Abstract

For further enhancement of critical currents density J c and irreversibility field H irr of (Cu 1− x C x ) Ba 2Ca n−1 Cu n O 2 n+4− δ ((Cu,C)-( n−1) n, n=3, 4 and 5) family, pinning centers were introduced by ion and neutron irradiation in these compounds. The polycrystalline samples were irradiated with 3.6×10 17 neutrons/cm 2 or with Au 15+ ions (240 MeV energy) at a fluence of 1×10 11 ions/cm 2. J c and H irr were determined for the irradiated samples as well as unirradiated samples. The intragrain J c was evaluated from M– H curves using Bean's critical state model. In (Cu,C)-12( n−1) n, J c (77 K, 1 T) shows a remarkable increase from 3.9×10 4 to 9.1×10 5 A/cm 2 for neutron irradiated (Cu,C)-1234 and from 3.9×10 4 to 4.1×10 6 A/cm 2 for heavy-ion irradiated (Cu,C)-1234. These results indicate the possibility of further enhancement of J c and of achieving a very high H irr of (Cu,C)-1234 in (Cu,C)-12( n−1) n family.