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arXiv · 0710.2151

Analytical investigation of magnetic field distributions around superconducting strips on ferromagnetic substrates

Yasunori Mawatari
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Abstract

The complex-field approach is developed to derive analytical expressions of the magnetic field distributions around superconducting strips on ferromagnetic substrates (SC/FM strips). We consider the ferromagnetic substrates as ideal soft magnets with an infinite magnetic permeability, neglecting the ferromagnetic hysteresis. On the basis of the critical state model for a superconducting strip, the ac susceptibility $χ_1'+iχ_1''$ of a SC/FM strip exposed to a perpendicular ac magnetic field is theoretically investigated, and the results are compared with those for superconducting strips on nonmagnetic substrates (SC/NM strips). The real part $χ_1'$ for $H_0/j_cd_s\to 0$ (where $H_0$ is the amplitude of the ac magnetic field, $j_c$ is the critical current density, and $d_s$ is the thickness of the superconducting strip) of a SC/FM strip is 3/4 of that of a SC/NM strip. The imaginary part $χ_1''$ (or ac loss $Q$) for $H_0/j_cd_s<0.14$ of a SC/FM strip is larger than that of a SC/NM strip, even when the ferromagnetic hysteresis is neglected, and this enhancement of $χ_1''$ (or $Q$) is due to the edge effect of the ferromagnetic substrate.

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Yasunori Mawatari. 2007-10-11. Analytical investigation of magnetic field distributions around superconducting strips on ferromagnetic substrates. https://doi.org/10.1103/physrevb.77.104505

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