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对吴杭生等人的计算公式做了适当的简化.可减小数值计算的工作量.不通过数值计算,直接估计了磁场能使偶数标号台阶高度增大的上限标号n、对2e/h测量中用加磁场来增大台阶高度是否有意义的问题做了讨论. 相似文献
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本文给出了在瞬变电磁法大地电磁测量中,在半空间均匀条件下高TcSQUID所探测到的二次场B(t)的解析表达式,将高TcSQUID与常规感应探头作了对比.结果展示了在长偏移距(LOTEM)方法和磁偶极源探测深埋层的大体积金属矿体时,高TcSQUID有明显的优越性. 相似文献
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The ground state of a two-dimensional square superconducting π
ring array has been investigated. The circulating currents of the
π ring array will spontaneously magnetize to the
`antiferromagnetic' arrangement with directions of the
nearest-neighbouring currents circulating oppositely in the absence
of an external magnetic field. It is found that the external magnetic
field could destroy the anti-parallel configuration effectively. The
external magnetic field needed to destroy the anti-parallel
configuration is related to the superconducting \pi ring's
inductance parameter β=2\pi L Ic/\phi0. For a small β
the anti-parallel configuration, which is the lowest-energy ground
state of the system, will be fully destroyed and changed to the
configuration that the circulating currents have the same direction
and parallel to the external magnetic field when the magnetic flux
reaches \phi0/4 in each ring. Moreover, the magnetic field needed
to destroy the anti-parallel configuration will be very small when
β is large enough. 相似文献
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We have studied the basic characteristics of a radio frequency superconducting quantum interference device (rf SQUID) involving two Josephson junctions connected in series, the case for the widely used grain boundary junction (GBJ) rf SQUID. It is found that the SQUID properties are determined mainly by the weaker junction when the critical current of the weaker junction is much lower than that of the other junction. Otherwise, the effect of the other junction is not negligible. We also find that only when the hysteresis parameter β is less than 1-α, where α is the critical current ratio of the two junctions, will the SQUID operate in the nonhysteretic mode. 相似文献
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We present the theoretical investigation of spontaneous magnetization of a coupled 2×2 πring array. It is indicated by free energy calculation that the system has the lowest energy when the four π rings have the full antiparallel configuration. Furthermore, the numerical evaluation results show that the system which favours full antiparallel spontaneous magnetization is a quantum effect deriving from the phase cohering of the superconducting quantum wavefunctions in the four superconducting rings through the shared Josephson junctions. 相似文献