Evidence for superconductivity above 40 K in the La-Ba-Cu-O compound system
An apparent superconducting transition with an onset temperature above 40 K has been detected under pressures in the La-Ba-Cu-O compound system synthesized directly from a solid-state reaction of ${\mathrm{La}}_{2}$${\mathrm{O}}_{3}$, CuO, and ${\mathrm{BaCO}}_{3}$ followed by a decomposition of the mixture in a reduced atmosphere. The experiment is described and the results of effects of magnetic field and pressure are discussed.