High-T_c superconductivity in new oxide systems

Superconducting transitions have been observed by resistivity measurements for several specimens of L-M-Cu-O system with L being Yb, Lu, Y, La and the mixture of Yb and La, and M being Ba and mixture of Ba and Sr. The onset transition temperature T_c becomes very close to 100 K. Since Yb-Ba-Cu-O and Lu-Ba-Cu-O have almost the same transition temperatures (T_c>90 K), the magnetic moment of Yb atoms does not seem to destroy the superconductivity in the present system. This suggests that the superconductivity occurs in certain parts of the system which are, at least, far from the Yb atom sites. Therefore M-Cu-O or Cu-O system may have an essential role in the occurrence of the superconductivity.