Influence of the doping on anisotropy of the transport properties in layered Nd-2-xCexCuO4+delta and Ca2-xSrxRuO4 single crystals

摘要

The investigation results of the in-plane rho(ab)(T) and out-of-plane rho(c)(T) resistivities (1.5K <= T <= 300K) of Nd2-xCexCuO4+delta single crystal films (x = 0.12; 0.15; 0.17) with (001) and (110) orientations and Ca2-xSrxRuO4 single crystals (0 <= x <= 2) are presented. For both stoichiometric reduced Nd2-xCexCuO4+delta (delta congruent to 0) and impurity doped Ca2-xSrxRuO4 systems, the conduction mechanism appears to be different between ab- and c- directions: a combination of in-plane metallic (d rho(ab)/dT > 0) and out-of-plane nonmetallic (d rho(c)/dT < 0) behaviour is a real evidence of the 2D-character conductivity in the systems investigated. The evolution from metallic (and superconducting) to dielectric system can be described as Anderson-type disorder-induced transition in a quasi-two-dimensional system. (c) 2005 Elsevier B.V. All rights reserved.