Superconducting thin films of (Cu,C)Ba$_2$Ca$_2$Cu$_3$O$_{9+\delta}$ with zero resistance transition temperature close to 100 K

Abstract

High superconducting transition temperature is favorable for the applications of superconductors. Some cuprate superconductors have the transition temperatures above 100 K, such as the Hg- or Tl-based 1223 and 1234 phases, but many of them contain the toxic elements, like Hg and Tl. Meanwhile, the high anisotropy makes the vortices easy to move, thus the irreversibility magnetic field is very low in the liquid nitrogen temperature region. Here we report the successful synthesis of superconducting thin films (Cu,C)Ba$_{2}$Ca$_{2}$Cu$_3$O$_{9+\delta}$ with the zero-resistance transition temperature reaching 99.7 K. The film shows a very good crystallinity with (00l) orientation. The superconducting transitions are rather sharp as revealed by both resistivity and magnetization measurements. Temperature dependent resistivity has been measured under different magnetic fields along c-axis and ab-plane, and the irreversibility lines have been achieved. The resistivity was also measured at different temperatures with the magnetic field rotated in the ac-plane, and the data can be nicely scaled by using the anisotropic Ginzburg-Landau model, yielding a temperature dependent anisotropy which varies from 17 at 110 K to 4 at 77 K. We also measured the magnetization-hysteresis-loops and calculated the critical current density through the Bean critical state model. The critical current density at 77 K is about 6$\times$10$^5$ A/cm$^2$ (zero field), thus the film may be a good candidate for the applications of superconducting cables or the high frequency superconducting filters.