Theory for measurements of penetration depth in magnetic superconductors by magnetic force microscopy and scanning SQUID microscopy

Shi-Zeng Lin; Lev N. Bulaevskii

doi:10.1103/PhysRevB.86.014518

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Theory for measurements of penetration depth in magnetic superconductors by magnetic force microscopy and scanning SQUID microscopy

Shi-Zeng Lin, Lev N. Bulaevskii

DOI 10.1103/PhysRevB.86.014518 · Physical Review B

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Abstract

The working principle of magnetic force microscopy and scanning SQUID microscopy is introducing a magnetic source near a superconductor and measuring the magnetic field distribution near the superconductor, from which one can obtain the penetration depth. We investigate the magnetic field distribution near the surface of a magnetic superconductor when a magnetic source is placed close to the superconductor, which can be used to extract both the penetration depth λL and magnetic susceptibility χ by magnetic force microscopy or scanning SQUID microscopy. When the magnetic moments are parallel to the surface, one extracts λL/1−4πχ. When the moments are perpendicular to the surface, one obtains λL. By changing the orientation of the crystal, one thus is able to extract both χ and λL.