We derive new expressions for the average magnetization loops, M(H), based on the exponential critical state model. The components χ′ and χ″ of the complex susceptibility are calculated and an algorithm to fit ac susceptibility data is discussed. This algorithm is employed to study the intergranular response χ′(Hm) and χ″(Hm) measured for two samples of YBa2Cu3O7−δ as a function of the ac field amplitude Hm. One sample is a porous sintered cylinder and the other is a very dense melt‐textured bar. In both cases good fits of the calculated components χ′ and χ″ are obtained using an algorithm that involves two free parameters, the full penetration field, Hp, and the sample quality factor, p. An interesting result for the melt‐textured sample is the observation of a step in χ′(Hm) curves at very low Hm, possibly associated with grain clustering.
Exponential critical state model applied to ac susceptibility data for the superconductor YBa2Cu3O7−δ
F. M. Araújo‐Moreira, W. A. Ortiz, O. F. de Lima; Exponential critical state model applied to ac susceptibility data for the superconductor YBa2Cu3O7−δ. J. Appl. Phys. 15 September 1996; 80 (6): 3390–3395. https://doi.org/10.1063/1.363204
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