HALL-EFFECT AND SUPERCONDUCTING PROPERTIES OF (ND0.8-XCEXSR0.2)2CUO4-DELTA WITH T-STAR STRUCTURE

Hall effect and superconducting properties of polycrystalline (Nd0.8-xCe(x)Sr0.2)2CuO4-delta compounds with the T* structure have been studied. The temperature dependence of the positive Hall coefficient has a broad maximum around 150 K. This indicates that simple single carrier models for normal metals do not apply. Three possibilities for the temperature dependence of the Hall coefficient are discussed, and a van Hove singularity near the Fermi level is the most plausible explanation for the temperature dependence. The upper, lower and thermodynamic critical fields obtained for (Nd0.7Ce0.1Sr.2)2CuO4-delta are 15, 0.04 and 0.11 T, respectively. A comparison with the results of T and T' phase materials suggests that the coherence length is closely associated with the structures of the CuO(n) polyhedra in cuprate superconductors.