Doping manganites by La-site vacancies and Ca ions: bulk ceramics and thinfilms

The effects of La manganite doping by Ca and A-site vacancies are compared in thin films and bulk ceramics. In bulk, rombohedric, orthorhombic or mixe d manganite crystallographic phases are found. depending on the Ca content. It is found that up to a certain level. the increase of Tc by Ca and vacan cy doping is cumulative. Maximum T-c obtained in bulk samples after oxygen annealing is limited by the optimum stoichiometric doping value (T-c simila r to 267 K for La0.67Ca0.33MnO3), but in thin films T-c up to 300 K are obt ained. The oxygen incorporation process is a crucial factor for the optimiz ation of T-c especially in vacancy-doped samples. (C) 2001 Published by Els evier Science B.V.