Epitaxial Growth and Characterization of Mid-frequency AC Reactive Magnetron Sputtered LaMnO₃ Cap Layer on MgO Templates

Reduction of manufacturing cost for YB₂ Cu₃O_7−δ (YBCO) coated conductors is one of the key issues for the commercialization of second-generation superconducting wire. In this work, a reel-to-reel magnetron sputtering system with mid-frequency alternating current (AC) power supply was utilized to provide a low cost and stable process for epitaxial growth of LaMnO₃ (LMO) films, which serve as the cap layer for YBCO functional films. The microstructure and surface morphology of LMO films were characterized by X-ray diffraction and atom force microscope. It was found that LMO template exhibited excellent crystalline quality with the full width at half-maximum values of 2.8^∘ and 2.4^∘ for the (220) LMO and rocking curve of (002) LMO, respectively. Morphology analysis revealed a smooth, dense, and crack-free surface. Highly epitaxial YBCO film on this template exhibited the high self-field critical current of 301 A/cm, corresponding to a calculated critical current density about 6 MA/cm² (500 nm).