Superconducting thin films of [formula omitted][formula omitted][formula omitted][formula omitted] 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 anisotropy of upper critical field or the effective mass of above mentioned Hg-, Tl-based systems, or the non-toxic Bi2Sr2Ca2Cu3O10 with Tc = 110 K is high, which makes the vortices easy to move and the irreversibility magnetic field is very low in the liquid nitrogen temperature region. Here we report the successful synthesis of the c-axis oriented (Cu,C)Ba2Ca2Cu3O9±δ superconducting thin film with the zero-resistance transition temperature reaching 99.7 K. The superconducting transitions are rather sharp as revealed by both resistivity and magnetization measurements. Temperature dependent resistivity has been measured under different magnetic fields, and the irreversibility lines have been achieved. The resistivity was also measured 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. Additionally, the critical current density calculated from the magnetization-hysteresis-loops reaches about 6×105A/cm2 (zero field) at 77 K. Thus the film may be a good candidate for the applications of superconducting cables or high frequency superconducting filters in liquid nitrogen temperature region.