The process of cold seeding melt growth of GdBa2Cu3Oy （Gd123） bulk superconductors using NdBa2Cu3Oy （Nd123） thin films was reported. In addition, a novel cold seeding concept of combining MgO crystal and buffer pe...The process of cold seeding melt growth of GdBa2Cu3Oy （Gd123） bulk superconductors using NdBa2Cu3Oy （Nd123） thin films was reported. In addition, a novel cold seeding concept of combining MgO crystal and buffer pellet was also introduced. The misorientation caused by the lattice mismatch between MgO and Gd123 melt was overcome by choosing suitable heat treatment program and Gd2BaCuO5 （Gd211） content of the buffer pellet. The doping effect of soft ferromagnetic NiFe alloy particles was also reported. The bulk sample with 0.4% （mole fraction） doping amount shows the best performance on the flux trapping. The critical current density is largely enhanced under the external field of 1-2 T, which is promising for large-scale applications. This effect is originated from the substitution of Fe and Ni ions for the Cu sites contributing to magnetic flux pinning.展开更多
We investigate the vortex dynamics in two typical hole doped iron based superconductors CaKFe_4As_4(CaK1144) and Ba_(0.6)K_(0.4)Fe_2As_2(BaK122) with similar superconducting transition temperatures. It is found that t...We investigate the vortex dynamics in two typical hole doped iron based superconductors CaKFe_4As_4(CaK1144) and Ba_(0.6)K_(0.4)Fe_2As_2(BaK122) with similar superconducting transition temperatures. It is found that the magnetization hysteresis loop exhibits a clear second peak effect in BaK122 in wide temperature region while it is absent in CaK1144. However, a second peak effect of critical current density versus temperature is observed in CaK1144, which is however absent in BaK122. The different behaviors of second peak effect in BaK122 and CaK1144 may suggest distinct origins of vortex pinning in different systems. Magnetization and its relaxation have also been measured by using dynamical and conventional relaxation methods for both systems. Analysis and comparison of the two distinct systems show that the vortex pinning is stronger and the critical current density is higher in BaK122 system. It is found that the Maley's method can be used and thus the activation energy can be determined in BaK122 by using the time dependent magnetization in wide temperature region, but this is not applicable in CaK1144 system.Finally we present the different regimes with distinct vortex dynamics in the field-temperature diagram for the two systems.展开更多
文摘The process of cold seeding melt growth of GdBa2Cu3Oy （Gd123） bulk superconductors using NdBa2Cu3Oy （Nd123） thin films was reported. In addition, a novel cold seeding concept of combining MgO crystal and buffer pellet was also introduced. The misorientation caused by the lattice mismatch between MgO and Gd123 melt was overcome by choosing suitable heat treatment program and Gd2BaCuO5 （Gd211） content of the buffer pellet. The doping effect of soft ferromagnetic NiFe alloy particles was also reported. The bulk sample with 0.4% （mole fraction） doping amount shows the best performance on the flux trapping. The critical current density is largely enhanced under the external field of 1-2 T, which is promising for large-scale applications. This effect is originated from the substitution of Fe and Ni ions for the Cu sites contributing to magnetic flux pinning.
基金supported by the National Key Research and Development Program of China(2016YFA0300401)the National Natural Science Foundation of China(A0402/11534005)
文摘We investigate the vortex dynamics in two typical hole doped iron based superconductors CaKFe_4As_4(CaK1144) and Ba_(0.6)K_(0.4)Fe_2As_2(BaK122) with similar superconducting transition temperatures. It is found that the magnetization hysteresis loop exhibits a clear second peak effect in BaK122 in wide temperature region while it is absent in CaK1144. However, a second peak effect of critical current density versus temperature is observed in CaK1144, which is however absent in BaK122. The different behaviors of second peak effect in BaK122 and CaK1144 may suggest distinct origins of vortex pinning in different systems. Magnetization and its relaxation have also been measured by using dynamical and conventional relaxation methods for both systems. Analysis and comparison of the two distinct systems show that the vortex pinning is stronger and the critical current density is higher in BaK122 system. It is found that the Maley's method can be used and thus the activation energy can be determined in BaK122 by using the time dependent magnetization in wide temperature region, but this is not applicable in CaK1144 system.Finally we present the different regimes with distinct vortex dynamics in the field-temperature diagram for the two systems.
