Comment on “London model for the levitation force between a horizontally oriented point magnetic dipole and superconducting sphere”

Qiong-Gui Lin

doi:10.1103/PhysRevB.75.016501

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Comment on “London model for the levitation force between a horizontally oriented point magnetic dipole and superconducting sphere”

Qiong-Gui Lin

DOI 10.1103/PhysRevB.75.016501 · Physical Review B

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Abstract

In a recent paper the magnetostatic boundary-value problem for a magnetic dipole with transverse direction in the presence of a superconducting sphere was solved in both cases when the London penetration depth is zero and finite. It was concluded that the levitation force on the transverse magnetic dipole is exactly half that for a magnetic dipole with radial direction. We show that this conclusion is incorrect in either case. In the former case it is due to an incorrect boundary condition. In the latter case it is caused by calculational errors. Corrected results are presented. The distribution of supercurrent and the associated magnetic moment are also calculated.