Flux Pinning Enhancements of YBa2Cu3O7-x with Nanosize Magnetic Additions

Abstract

Different methods of flux pinning are being tested world-wide to enhance critical currents (I_cs) of high temperature superconductor YBa₂Cu₃O_7-x (YBCO) coated conductors exposed to high magnetic fields. Magnetic materials are interesting to consider as flux pinning additions because of their potential for very strong pinning strength. To our knowledge, there have been limited demonstrations of magnetic pinning additions to YBCO conductors. This paper describes the study of different M magnetic phase additions to YBCO including M = BaFe₁₂O₁₉, La_0.67Ca_0.33MnO₃, and other oxide phases. Nanosize additions were incorporated by depositing multilayer (M/YBCO)_N films to minimize degradation of T_c, and testing volume % additions of M phase from 0.5 % to 5%. Results indicate that T_c onsets are depressed with magnetic additions, however in some cases interestingly without degrading the transition width. With optimization of magnetic additions a 50% increase of critical current density has been obtained, for low magnetic fields of < 10,000 Oe at 65K to 77K. Microstructural and superconducting properties are summarized, including SEM analysis.