Correlation between superconducting transition width and relaxation rates in various industrial Y123-coated conductors

Measurements of the time decay of non-equilibrium magnetization of various industrial Y123-coated conductors have been performed in a dc magnetic field up to 9 T, at temperatures varying from 5 to 50 K. In addition, the temperature dependence of the zero-field-cooled (ZFC) magnetization has been studied in order to determine the width of the Tc distribution and thus the homogeneity of the superconducting layer. The most stringent condition for applications of superconductors in high field NMR magnets is the ability to operate in persistent mode, which requires a low relaxation rate as a function of time for the supercurrent. Relaxation rates of Y123-coated conductors were found to be comparable to those of Nb3Sn at 4.2 K in a wide range of temperatures and magnetic fields. In particular, for one of the examined coated conductors, relaxation rates are ≤2.2%/decade of the time log-scale up to T = 50 K and B = 6 T. In this paper it is shown that the width of the Tc distribution is strongly influenced by the deposition method of the superconducting layer. It is concluded that the inhomogeneities leading to the broadening of the superconducting transition are directly responsible for the improvement of the pinning properties.