Superconductivity and Magnetism in the La 2 CuO 4 -Based Compounds
- PDF / 1,365,493 Bytes
- 4 Pages / 604.8 x 806.4 pts Page_size
- 86 Downloads / 180 Views
Superconductivity and Magnetism in the La2Cu04-Based Compounds Z. Fisk, S-W. Cheong, and D.C. Johnston Crystal Chemistry of L a 2 C u 0 4 La 2 CuO, crystallizes in an orthorhombic distortion of the tetragonal K2NiF4 structure, a so-called layered perovskite. The important question here concerns the stoichiometry of La 2 Cu0 4 prepared by various techniques. Regarding the La and Cu sites, recent neutron diffraction studies of powders have shown that the La:Cu ratio can vary from 2:1 by S l % in various preparations. 1 2 Single crystals have been g r o w n variously from CuO, PbO and Li 2 0-B 2 0 3 fluxes. The last two fluxes incorporate some Pb and Li, respectively, into the crystals, but the cation ratio is found to be 2:1 within the accuracy of x-ray refinement. It is also known that the oxygen stoichiometry 1 " 4 corresponds to La 2 Cu0 4 within = 1 % . Extensive a n d precise magnetic susceptibility (x) and other studies of p o w d e r samples s h o w e d , however, that the physical properties are extremely sensitive to
Data Loading...
