A Comparative Study of Nonlinear Microwave Properties in ${\rm YBa}_{2}{\rm Cu}_{3}{\rm O}_{7}$ , TlBaCaCuO and HgBaCaCuO Microstrip Resonators

Microwave nonlinearity is investigated in several high-temperature superconductors (HTS) including YBa₂Cu₃O₇, TlBa₂CaCu₂O₇, Tl₂Ba₂CaCu₂O₈ , TlBa₂Ca₂Cu₃O₉ and HgBa₂CaCu₂O_6+delta microstrip resonators. The critical power P _c, above which nonlinearity becomes a serious concern, was compared with the dc critical current density J _c at temperatures above 77 K. When plotted at the real temperature scale, Pc and J _c for each HTS system follow a similar trend near T _c, indicating that a similar mechanism of magnetic pinning limits both P _c and J _c. This result suggests that a better Pc may be achieved in HTS films of enhanced magnetic pinning.