抄録
Correlated pinning properties for GdBa2Cu3O7 (Gd123) tapes with BaHfO3 and BaZrO3 nanorods are investigated on the basis of the detailed critical current measurements in a wide temperature and magnetic field region. We found that a magnetic field dependency of Jc for the Gd123 tapes with nanorods introduced changes around the matching field B while that for the non-doped Gd123 tapes is proportional to B-0.56 in a wide field region below 20 K. These experimental results suggest that the nanorods are still effective as the c-axis correlated pinning center at low temperatures, although the Jc peaks at B//c in its angular dependency disappear below 20 K at 3 T. The cooperative model of random and correlated pinning centers indicates that the c-axis peaks in angular dependency of Jc disappear when fluctuation of the nanorods' growth direction is large. Therefore, the nanorods are effective as the c-axis correlated pinning centers even at low temperatures around 4.2 K, although their contribution becomes small.
