The first superconducting thin film oxycarbonates coherent intergrowth of several members of a new structural series (CaCuO2)m (Ba2CuO2CO3)n

Abstract Superconducting thin films of copper oxycarbonates have been synthesized for the first time using laser ablation. The resistance measurements show a broad transition with T c onset ranging from 80 to 100 K and zero resistance below 60 K. Magnetic measurements indicate diamagnetism below 58 K in the best film. The ED and HREM studies show that these new oxycarbonates are tetragonal with a ∼ a p and c ∼ ( m + 2) × a p , and that the films consist of an intergrowth of serveral members of a family with the general composition (CaCuO 2 ) m (Ba 2 CuO 2 CO 3 ) n . The main member that forms the matrix, Ba 2 Ca 3 Cu 4 CO 3 O 8 ( m = 3; n = 1), consists of double layers of CuO 4 groups sandwiched by pyramidal copper layers and interconnected with layers of CO 3 groups. In a general way, the different members of the series can be described as the intercalation of layers of carbonate groups in the infinite-layer structure CaCuO 2 . The origin of superconductivity and the relationships with bulk “BaCaCu” oxycarbonates that are prepared at high pressure are discussed.