Magnetic field alignment of high-Tc superconductorsRBa2Cu3O7–δ (R=rare earth)
Magnetic field alignment of high-Tc superconductorsRBa2Cu3O7–δ (R=rare earth)
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高温超导体RBa2Cu3O7–δ（R=稀土）的磁场排列
DOI：
10.1007/bf00619708
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
R. P. Guertin
中科院分区：
文献类型：
--
作者：
J. M. Ferreira;J. M. Ferreira;M. Maple;H. Zhou;R. Hake;R. Hake;Bo Wha Lee;C. L. Seaman;M. Kuric;R. P. Guertin
将RBa 2Cu 3 O 7 − δ（R=Y、Nd、Sm、Eu、Dy、Ho、Er、Tm、Yb）的细粉以3%的体积浓度稀释后混合到环氧树脂基体中，然后使其在HA =18 kOe的磁场中硬化。X射线衍射研究和4.3 K超导感应磁滞回线ΔM的测量结果表明，单晶晶粒c轴至少部分取向：（1）当R =Y，Nd，Sm，Dy，Ho时，c轴平行于HA（Farrell等人早期发现的R =Y）;（2）当R =Eu，Er，Tm，Yb时，c轴垂直于HA。除了少数例外（Y，Sm，Eu）的取向方向与晶体电场哈密顿量的二阶Stevens因子αJ的符号相关，其方式由利文斯顿等人提出。对于最佳取向试样（Ho，Dy），临界电流密度Jc（4.3 K，5 kOe）由ΔM和Bean模型估计，对于平行于原始取向场HA的测量场H，单个晶粒的ΔM和Bean模型为107 A/cm 2量级，垂直于HA方向的H为106 A/cm ~ 2量级。
Finely ground powders ofRBa2Cu3O7 − δ (R=Y, Nd, Sm, Eu, Dy, Ho, Er, Tm, Yb) have been mixed at dilute 3%-by-volume concentrations into epoxy matrices which were then allowed to harden in applied magnetic fieldsHA=18 kOe. X-ray diffractometry studies and 4.3 K measurements of supercurrent-induced magnetization hysteresisΔM are interpreted as indicating at least partial alignment of single-crystal-grain c-axes (1) parallel toHA forR=Y, Nd, Sm, Dy, Ho (as earlier found by Farrell et al. forR=Y), and (2) perpendicular toHA forR=Eu, Er, Tm, Yb. With a few exceptions (Y, Sm, Eu) the alignment direction correlates with the sign of the second-order Stevens factorαJ of the crystalline electric field Hamiltonian in the manner suggested by Livingston et al. For the best aligned specimens (Ho, Dy) critical current densitiesJc (4.3 K, 5 kOe) for individual grains are estimated fromΔM and the Bean model to be of order 107 A/cm2 for the measuring fieldH parallel to the original alignment fieldHA, and of order 106 A/cm2 forH perpendicular toHA.