Characteristic properties of doped Bi2212 single crystals studied by magneto optical measurement
Characteristic properties of doped Bi2212 single crystals studied by magneto optical measurement
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磁光测量研究掺杂Bi2212单晶的特性
DOI：
10.1109/tasc.2003.812541
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发表时间：
2003
影响因子：
1.8
通讯作者：
K. Kishio
中科院分区：
文献类型：
--
作者：
T. Okabe;J. Shimoyama;M. Shigemori;S. Horii;K. Kishio
为了阐明Pb掺杂对晶内J/sub c/特性的本质影响，对具有均匀微结构的轻掺Pb Bi 2212单晶在H /spl par/ c条件下的局部J/sub c/分布进行了研究。在25 K以下，在恒定磁场H/sup */下，观察到Bi（Pb）2212单晶的内场梯度突变。J/sub c/明显高于H/sup */。在几百Oe处观察到H/sup */，其远低于磁化磁滞回线中的第二峰值场H/sub pk/。这表明，随着内磁场的增加，在H/sup */处，涡旋的维数从3D态变为准2D态，这可能是由于铅离子在晶体中的不均匀分布所致.高于H/sup */和温度依赖性H/sub pk/的更高的J/sub c/表明在本系统中产生场诱导钉扎位点。研究了Co掺杂对重掺Pb Bi 2212单晶磁通钉扎性能的影响。发现随着Co掺杂水平的增加，面内J/sub c/变得各向同性。
Local J/sub c/ distribution under H /spl par/ c was carefully investigated for lightly Pb-doped Bi2212 single crystals having uniform microstructure in order to clarify essential effect of Pb-doping on intra-grain J/sub c/ properties. An abrupt change of internal field gradient was observed at a constant field, H/sup */, for each Bi(Pb)2212 single crystal below 25 K. J/sub c/ is apparently higher above H/sup */. The H/sup */ was observed at several hundred Oe which was much lower than the second peak field, H/sub pk/, in the magnetization hysteresis loops. This suggested that dimensionality of vortex changed at H/sup */ from 3D to quasi-2D state with an increase of internal magnetic field, possibly due to an inhomogeneous distribution of lead ions in the crystal. Higher J/sub c/ above H/sup */ and temperature dependent H/sub pk/ indicated generation of field-induced pinning sites in the present system. Doping effects of cobalt for heavily Pb-doped Bi2212 single crystals on the flux pinning properties were also studied. In-plane J/sub c/ was found to become isotropic with increasing the Co-doping level.