Superconducting phases, charge ordering and possible correlation between them in La2CuO4.12

Superconducting phases, superstructural modulations and their relationship in La2CuO4.12 were studied. By magnetic measurements and x-ray diffraction, two superconducting phases with T-c values of 15 and 41 K were found with the structurally independent correspondents of two orthorhumbic Fmmm phases . By electron diffraction, two types of superstructural modulations situate d on the ab- and bc-plane were observed, with modulation vectors of 1/6a* /- 1/2b* and 0.18b* +/- (0.26-0.28)c*, respectively. These superstructural modulations were identified to be actually originated from two types of cha rge ordering. In addition, it is indicated that the observed ab- and bc-pla ne charge ordering could very possibly be correlated to the 15 and 41 K pha ses, respectively. For the 15 K phase, its depressed superconductivity poss ibly originates electronically from the ab-plane charge ordering which is c ompatible with the concept of the 'stripe phase'.