Scaling Law on the temperature and magnetic field dependence of critical current density in the mixed state of superconductors

1. 在假定G-L跃迁附近的E对J的标度定律可以近似地应用到较低的温度下，利用我们提出的玻璃-液相变的广义理论，导出了高温铜超导体在电场E=E_c处观察到的临界电流密度J_c对温度T和通量密度B的依赖关系的理论表达式。结果表明，高温铜超导体中J_c的T和B依赖的标度规律的推导表达式与金属超导体的标度规律有明显的不同。通过输运测量，研究了柱状缺陷密度对PLD法制备YBa_2Cu_3O_7薄膜钉钉参数的影响。为了在可控的情况下人工产生缺陷，重离子被照射到薄膜上。临界电流密度j_c_i…More随着辐照剂量的增加而增加，这是由于在样品中引入了强钉钉位点。这些结果可以用渗流模型描述为受诱导缺陷影响的钉钉强度分布的变化。采用PLD法制备了含有BaZrO_3（BZO）纳米棒的ErBa_2Cu_3O_y （ErBCO）薄膜，提高了临界电流密度J_c。含有1.5wt% BZO （Er15）的ErBCO薄膜在磁场中的J_c值高于含有0.5wt% BZO （Er05）的ErBCO薄膜。当平行于c轴施加磁场时，在两种薄膜中都观察到J_c的角依赖性峰。发现该峰值是由平行于c轴取向的BZO纳米棒的磁通钉住引起的。在磁场依赖性中观察到钉钉参数的峰值。这可能是由于BZO纳米棒的密度与流体的密度相匹配，TEM观测证实了这一点。少

1. A theoretical expression for the dependences on the temperature, T, and the flux density, B, of the critical current density, J_c, observed at the value of the electric field E=E_c in the high temperature cuprate superconductors was derived by using a generalized theory of the Glass-Liquid Transition proposed by us, under the assumption that the scaling law of E against J near the G-L Transition can be approximately applied down to fairly low temperatures. It is shown that the derived expression for the scaling law for the T and B dependences of J_c in the high temperature cuprate superconductors is noticeably different from that for the metallic superconductors.2. We have studied the effect of the densities of columnar defects on pinning parameters in YBa_2Cu_3O_7 thin films prepared by the PLD method with the transport measurements. In order to produce the defects artificially in a controlled manner, the heavy-ions were irradiated onto the films. The critical current density J_c i … More ncreases with the doses of the irradiation due to the introduction of the strong pinning sites into samples. These results could be described by the percolation model as a variation of pinning strength distribution affected from the induced defects.3. ErBa_2Cu_3O_y (ErBCO) thin films with BaZrO_3(BZO) nano-rods were prepared by a PLD method for an enhancement of critical current density J_c. The values of J_c for the ErBCO thin film containing 1.5wt% BZO (Er15) in magnetic fields are higher than those for the ErBCO thin film containing 0.5wt% BZO (Er05). The peaks of J_c have been observed in the angular dependence of J_c in both the films when the magnetic field is applied parallel to the c-axis. It has been found that the peak is attributed to the flux pinning by BZO nano-rods oriented parallel to the c-axis. The peak of the pinning parameter has been observed in the magnetic field dependence. This fact is probably due to the matching the density of BZO nano-rods with that of fluxoids, which was confirmed by TEM observations. Less