Inductive measurements of third-harmonic voltage and critical current density in bulk superconductors

Yasunori Mawatari; Hirofumi Yamasaki; Yoshihiko Nakagawa

doi:10.1063/1.1625423

paper

Inductive measurements of third-harmonic voltage and critical current density in bulk superconductors

arXiv:cond-mat/0307271 · doi:10.1063/1.1625423

Abstract

We propose an inductive method to measure critical current density $J_{c}$ in bulk superconductors. In this method, an ac magnetic field is generated by a drive current $I_{0}$ flowing in a small coil mounted just above the flat surface of superconductors, and the third-harmonic voltage $V_{3}$ induced in the coil is detected. We present theoretical calculation based on the critical state model for the ac response of bulk superconductors, and we show that the third-harmonic voltage detected in the inductive measurements is expressed as $V_{3} = G_{3} ω I_{0}^{2} / J_{c}$ , where $ω /2 π$ is the frequency of the drive current, and $G_{3}$ is a factor determined by the configuration of the coil. We measured the $I_{0}$ - $V_{3}$ curves of a melt-textured $YB a_{2} C u_{3} O_{7 - δ}$ bulk sample, and evaluated the $J_{c}$ by using the theoretical results.

3 pages, 1 figure, submitted to Appl. Phys. Lett