Measurement of Critical Currents in Superconducting Thin YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ Films by the Magnetic Susceptibility Method Using Open-Faced Coils
 作者： A. A. Kalenyuk, G. G. Kaminskyi, A. V. Semenov, V. O. Moskaliuk, V. S. Flis 作者单位： 1G.V. Kurdyumov Institute for Metal Physics, NAS of Ukraine, 36 Academician Vernadsky Blvd., UA-03680 Kyiv-142, Ukraine 2Institute of Physics, NAS of Ukraine, 46 Nauky Ave., 03028 Kyiv, Ukraine 刊名： Metallofiz. Noveishie Tekhnol., 2017, Vol.39 (4), pp.441-455 来源数据库： G.V. Kurdyumov Institute for Metal Physics, National Academy of Science of the Ukraine DOI： 10.15407/mfint.39.04.0441 关键词： critical current;  critical temperature;  magnetic susceptibility in an alternating field;  critical state model;  superconductor.; 原始语种摘要： The nonlinear magnetic susceptibility $\chi$($H_{\textrm{ac}}$) and critical current $J_{\textrm{c}}$ in thin YBa$_2$Cu$_3$O$_{7-\delta}$ films are measured using planar spiral open-faced pick-up coils. The real and imaginary parts of a generalized susceptibility $\tilde{\chi}(a, h)$ are calculated within the framework of the critical state model for an arbitrary ratio $a = r/R$ of the radius of a single-turn pick-up coil $r$ to the superconducting thin-film disc radius $R$. Well known results of the Clem–Sanchez model in the limit $a \to \infty$ are reproduced for nonlinear complex magnetic susceptibility $\chi$($h$), where $h$($J_{\textrm{c}}$($T$), $H_{\textrm{ac}}$) is reduced dimensionless field amplitude. Relative systematic error of measured $J_{\textrm{c}}$ is shown to be... negligible (< 2%) in a standard experimental geometry (with a sample within the pick-up coil of magnetometer) for $a > 2$, but it is of about 25% at $a \to 1$. On the other hand, for the open-faced coils with $a < 1$, the nature of amplitude dependences of $\tilde{\chi}$($a$, $h$) is changed qualitatively, turning to have threshold on $h$. That is why, at the fixed field amplitude $H_{\textrm{ac}}$, not unique point of the $J_{\textrm{c}}$($T$) dependence (at the maximum of $\chi^{''}$($T$, $H_{\textrm{ac}}$)) but two points (at both the maximum and the threshold of $\tilde{\chi}$$^{''}$($T$, $H_{\textrm{ac}}$)–$T$ dependence) can be obtained. This also simplifies the normalization procedure of the real and imaginary parts of generalized magnetic susceptibility.

• Cu
• susceptibility　磁化率
• delta　三角洲
• tilde　代字号
• generalized　广义
• imaginary　假想的
• dependence　从属
• magnetometer　地磁仪
• critical　临界的
• maximum　最大值