Levitation Force Between a Point Magnetic Dipole and Superconducting Sphere

The magnetic interaction between a point dipole and a superconducting sphere in the Meissner state is investigated in detail. It is demonstrated that the special case of perfect flux exclusion can be solved by the method of images when the dipole is vertically magnetized. The incorporation of a nonzero penetration depth is then made by developing the solution within London theory. The analytic solution, given in terms of an infinite series representation, is refined by exactly summing the perfectly diamagnetic response. Throughout, special cases of physical interest are discussed and applications to magnetic force microscopy and levitation are described.     

Levitation Force between a Horizontally Oriented Point Magnetic Dipole and a Superconducting Sphere

The magnetic interaction between a point dipole of horizontally oriented moment and a superconducting sphere in the complete Meissner state is investigated in detail. It is demonstrated that the levitation force for this configuration is precisely one half the value of the configuration with vertically oriented point dipole. An extension to other applied fields, still assuming the perfect flux exclusion state, is presented. The results have application to models for magnetic levitation and magnetic force microscopy.     

An Inverse Problem for the ac Magnetic Force Microscopy of Superconductors

A basic inversion problem for the magnetic force microscopy (MFM) of a semiinfinite superconductor in the Meissner state is formulated, ac Detection is assumed, with the MFM tip oscillating at angular frequency Ω. The coupling of all electrodynamic fields is treated, including a normal-current density in the superconductor. Under certain assumptions on the tip and superconductor geometry, a unique penetration depth λ(z) can be recovered from onedimensional force gradient measurements. This development opens new possibilities for the nondestructive evaluation of superconducting crystals and films.     

立式锌锅高频磁场悬浮力和封流特性研究

本文采用专门设计的悬浮力和电磁封流实验装置,在铜、铝、锌高频磁场电磁悬浮力研究的基础上,讨论了电磁封流影响因素,得出了铜、铝、锌三种金属在固态和液态的不同工艺参数的影响规律,讨论了立式锌锅高频磁场电磁封流的可行性。