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Evaluation method for flux pinning properties in the mixed state of superconductors

超导体混合态磁通钉扎性能评价方法

基本信息

批准号：
18560309
负责人：
FUJIYOSHI Takanori
金额：
$ 2.37万
依托单位：
Kumamoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

1. As-grown MgB_2 thin films on Si substrates with high J_c under magnetic fields were prepared by electron-beam evaporation. The value of J_c has been enhanced by the deposition of MgB_2 thin film in an O_2 atmosphere. The MgB_2 thin film deposited in the O_2 atmosphere O_2-doped film has exhibited considerably higher J_c in magnetic fields among MgB_2 thin films reported before. It has been found that the high J_c of the O_2-doped film is attributable to the flux pinning with grain boundaries strengthened by an introduction of MgO along grain boundaries. In a high magnetic field, a peculiar behavior of E-J characteristics where E-J curves vary in two stages was observed. This behavior also originates from the flux pinning with strengthened grain boundaries.2. Flux pinning properties in ErBa_2Cu_3O_y and YBa_2Cu_3O_y thin films with BaZrO_3 nano-rods prepared by PLD were measured to investigate the flux pinning mechanism. The enhancement of J_c was confirmed by the measurement of the dependence of J_c on magnetic field. The angular dependence of J_c has a broad peak at B‖c-axis. This result indicates that the BaZrO_3 nano-rods work as the c-axis-correlated pinning centers. The pinning parameter m was evaluated from the electric fields versus current density characteristics and the peak of m appears in the magnetic field dependence. The characteristic behavior of m is caused by the matching of the density of BaZrO_3 nano-rods with that of fluxoids. It is found that the relative distribution width of the local critical current density for the ErBa2Cu_3O_y film with BaZrO_3 nano-rods is smaller than that of the YBa_2Cu_3O_y films with BaZrO_3 nano-rods.

1.采用电子束蒸发法在磁场作用下在高J_c的Si衬底上生长了MgB_2薄膜。在O_2气氛中沉积了MgB_2薄膜，提高了J_c。在已有的报道中，在氧气气氛中制备的掺氧薄膜具有较高的J_c。结果表明，O_2掺杂薄膜的高J_c是由于沿晶界引入MgO强化了晶界的磁通钉扎作用。在强磁场下，观察到E-J特性的特殊行为，E-J曲线分两个阶段变化。这一行为还源于强化晶界的磁通钉扎作用。测试了用PLD法制备的BaZrO_3纳米棒掺杂的ErBa2Cu3Oy和YBa2Cu3Oy薄膜的磁通钉扎特性，探讨了磁通钉扎机理。测量了J_c随磁场的变化关系，证实了J_c的增强。J_c的角度依赖关系在B‖c轴处有一个宽峰。这一结果表明，BaZrO_3纳米棒起着c轴相关钉扎中心的作用。钉扎参数m由电场与电流密度的关系得到，m的峰值出现在磁场依赖关系中。M的特征行为是由于BaZrO_3纳米棒的密度与助熔剂的密度匹配所致。结果表明，含BaZrO_3纳米棒的ErBa2Cu3O_y薄膜的局域临界电流密度的相对分布宽度小于含BaZrO_3纳米棒的YBa2Cu3O_y薄膜。