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

1.本文利用我们提出的玻璃-液体转变的广义理论，导出了高温铜氧化物超导体在电场E=E_c时的临界电流密度J_c与温度T和磁通密度B的关系式。假设在G-L转变附近E对J的标度律可以近似地应用到相当低的温度。结果表明，高温铜氧化物超导体中J_c与T和B的标度关系式与金属超导体中的标度关系式明显不同.用输运测量方法研究了PLD法制备的YBa_2Cu_3O_7薄膜中柱状缺陷密度对钉扎参数的影响。为了以可控的方式人为地产生缺陷，将重离子照射到膜上。临界电流密度J_c i 关于我们 随着辐照剂量的增加，由于强钉扎位点的引入，这些结果可以用逾渗模型描述为诱导缺陷对钉扎强度分布的影响.为了提高临界电流密度Jc，采用PLD法制备了掺杂BaZrO 3（BZO）纳米棒的ErBa 2Cu 3 Oy（ErBCO）薄膜。含1.5wt%BZO（Er_（15））的ErBCO薄膜在磁场中的J_c值比含0.5wt%BZO（Er_（05））的高。当外加磁场平行于c轴时，两种薄膜的J_c随角度的变化均出现J_c峰。已经发现，该峰归因于平行于c轴取向的BZO纳米棒的磁通钉扎。钉扎参数的峰值已被观察到的磁场依赖性。这一事实可能是由于BZO纳米棒的密度与类流体的密度相匹配，这一点通过TEM观察得到证实。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