Flux pinning properties in Bi2Sr2CaCu2Oy single crystals and the effect ofintroducing nano-size MgO particles

The pinning properties in Bi(2212) single crystals prepared by the large te mperature-gradient technique are reported in comparison with that of 5% MgO nano-size particle added Bi(2212) crystals. We studied the scaling of volu me pinning force density F-p to the irreversibility field B-irr as the scal ing field parallel to the c-axis for these Bi(2212) crystals in low tempera ture from 18 Ii to 30 K. It was found that for the MgO added crystals the n ormalized F-p was scaled to temperature but for a single crystal no scaling was observed for the irreversible field B-irr obtained from the field depe ndence of irreversibility temperature. When a field B which gives one perce nt of the maximum pinning force density F-pmax was substituted for B-irr F- p/(pmax) in single crystal scaled with B/B. We discussed the origin of disa greement between the irreversibility field B-irr and field B in a single cr ystal and the effect of the MgO addition to the Bi(2212) crystal. Critical current of the Bi(2212) crystal in low temperature region could be improved by the 5% addition of the MgO nano-size particles.