Magnetization of a superconducting epitaxial (Y0.8Ca0.2)Ba2Cu3Ox film with O2 anneal

A c-axis epitaxial film of composition (Y0.8Ca0.2)Ba2Cu3O6+x is found to be superconducting over a wide range of oxygen stoichiometry, from x∼0 to x∼1.0. The oxygen stoichiometry was varied systematically by annealing films over four decades of oxygen partial pressure, ranging from 0.0067%--100% O2. Both the superconducting transition temperature and the remanent magnetization increase with increasing x and are approximately linear with log oxygen partial pressure over three decades. These increases are attributed mainly to the change in the number of holes in the Cu--O planes caused by oxidation