Effect of nonstoichiometric disorder on the transport properties of Nd 2− xCe xCuO 4+ δ single crystal films

Abstract

The effect of doping and nonstoichiometric disordering on the anisotropy of resistivity of Nd 2− x Ce x CuO 4+ δ single crystal films ( x=0.12; 0.15; 0.17) with (0 0 1) and (11̄0) orientations was investigated. We have found that the increase in the nonstoichiometric disorder leads to the growth of resistivity and to the change in the temperature dependence of the in-plane resistivity from ρ ab ( T)∼ T 2 to ρ ab ( T)∼exp( T/ T 0) −1/2. For most stoichiometric reduced films the conduction mechanism appears to be different between ab- and c-directions: a combination of in-plane metallic (d ρ ab /d T>0) and out-of-plane nonmetallic (d ρ c /d T<0) behavior is a real evidence of the 2D-character of the system investigated. The crossover from 2D to 3D was demonstrated to take place with increasing nonstoichiometric disorder.