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Highlights: [•] We calculate Meissner ac susceptibility of square film as a function of Pearl length. [•] New technique is developed for determining London penetration depth of square films. [•] The technique does not require special instrumentation and complex calculations. [•] Intrinsic and applied superconducting properties may be studied for the same film. [ABSTRACT FROM AUTHOR]

Abstract: A set of analytic expressions for the critical-state magnetization and ac susceptibility curves of rectangular superconducting films of arbitrary aspect ratio in perpendicular field is obtained. They are formulated based on the exact/accurate high/low-field limits for rectangular films together with the exact analytic formulas for thin circular disks. Thus, the accuracy of the expressions is very high in high and low fields. At a characteristic intermediate field amplitude, where takes its maximum, the error is checked by direct numerical calculations to be well below 1%. Thus, the provided expressions can be conveniently and satisfactorily used for practical and theoretical researches of superconducting materials, such as coated conductors. [Copyright &y& Elsevier]

Abstract: The perpendicular susceptibility of completely shielded elliptical and rectangular superconducting films with different aspect ratios has been calculated accurately. The obtained may be compared with the measured low-field limit of ac susceptibility to check the quality of superconducting films, and used as a scaling parameter to obtain field amplitude dependent complex critical-state ac susceptibility. [Copyright &y& Elsevier]

Abstract: The ac susceptibility of a type-II superconducting thin film divided into two halves by a narrow mid region with a smaller value of critical-current density is calculated by a model based on Bean’s critical-state model and energy minimization. Results are compared to measurements of ac susceptibility as a function of ac-field amplitude of artificial bicrystal-like films prepared by photolithography patterning a gridline of holes on epitaxial YBCO thin films. A qualitative agreement is found between calculated and experimental results. [Copyright &y& Elsevier]