Low-Field High-Harmonic Studies in Hg-1223 High-Temperature Polycrystalline Superconductor

We have studied harmonic generation in the ultra-weak magnetic fields of bulk sample of the HgBa2Ca 2Cu 3O8+δpolycrystalline superconductor. Dependence of the odd and even harmonics on the dc magnetic field, amplitude of the ac magnetic field, and the temperature was investigated. We observe very high-order odd harmonics generation when H=0. When dc field H≠0 is applied, even harmonics also appear and shape of the odd harmonics does not change. Our experiments show that the amplitudes of the odd harmonics squarely depend on the magnitude of the dc field. Numerical results of our experiments have demonstrated that the Jc=Jc(0)H02/H+H02\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$J_{c}=J_{c}(0)H_{0}^{2}/\left (H+H_{0}^{2}\right )$\end{document} critical-state theoretical model is preferable for investigating the sample.