抄録
For the study of magnetic properties of high-Tc superconductors, we measured harmonic ac susceptibilities Xn=Xn-iXn " of a single-crystal YBa2Cu3O7-d thin film immersed in an external field H(t)-Hde+Hey cos(ωt), where Mc (≥0) is a do bias field and Hac (> 0) is an ac field amplitude. Measurements of Xn were carried out for n=1, 2, 3, 5, 7 and μ0Hac=0.1mT. The fundamental frequency was 132Hz. The observed results were analyzed within the construct of the Kim-Anderson model for critical-current density and the modified Bean model which takes into consideration the surface barrier and the lower critical field. The characteristics of the experimental results were well reproduced by the modified Bean model, suggesting that the surface barrier plays an essential role for the thin film.
