Critical fields and critical currents of superconducting disks in transverse magnetic fields

Milind N. Kunchur; S. J. Poon

doi:10.1103/PhysRevB.43.2916

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Critical fields and critical currents of superconducting disks in transverse magnetic fields

Milind N. Kunchur, S. J. Poon

DOI 10.1103/PhysRevB.43.2916 · Physical Review B

T1

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Abstract

The large nonuniform and field-dependent demagnetizing factors of superconducting disks in transverse magnetic fields complicates the determination of the lower critical field and critical current from magnetization. Correcting the applied field with a constant ellipsoidally approximated demagnetization correction D′ can result in significant errors. In this study of the magnetization characteristics of lead and Nb-Ti disks with various aspect ratios a, we find an empirical relation D′(a) that describes the scaling of the applied-field value Hc′ (Hc1′), at which flux penetration occurs, with respect to the intrinsic (lower) critical fields Hc (Hc1). A model is described for determining Hc1 and Jc for such a geometry. The results have important implications for various magnetic measurements in high-Tc superconductors. The errors that can result in the measured values of Hc1 and Jc, in the inferred penetration depths, and in the effective-mass anisotropies, are discussed.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Nb-Ti Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	9	Pressure not reported	unknown