Crucial role of oxygen-deficient LaMnO3-delta cap buffer layer in enhancement of current carrying capability of MOD-YBCO coated conductors

LaMnO3-delta (LMO) films with different oxygen contents are deposited on Epi-MgO/IBAD-MgO templates using reactive magnetron sputtering under varying temperatures and atmospheres. Subsequent YBa2Cu3O7-delta (YBCO) films are grown on LMO layers by metal-organic deposition (MOD) method. X-ray diffraction measurements reveal that YBCO texture cannot be further improved when the full width at half maximum (FWHM) values of LMO (011) phi-scans (evaluation on in-plane alignment) and LMO (002) omega-scans (evaluation on out-of-plane alignment) for LMO films are less than 8 degrees and 4 degrees, respectively. Sharp orientation with in-plane FWHM value of <3 degrees for YBCO (103) phi-scan and out-of-plane FWHM value of <1.5 degrees for YBCO (006) omega-scan can typically be achieved in YBCO films. Precise control of growth conditions, especially atmosphere, remains a feasible way to modify the surface of LMO films. It induces changes in oxygen content, lattice structure and surface morphology of LMO, and further affects the epitaxial growth of superconducting layers. Oxygen-deficient LMO with expanded lattice parameters and flat surface can effectively suppress the non-c-axis oriented YBCO, thereby enhancing the current carrying capability. The 500 m long YBCO coated conductors with conditioned LMO layers have an inductive critical current (I-c) ranging from 358 to 437 A/12 mm width with an average value of 398 A/12 mm width.