Localization and superconductivity in single crystals of Sm 2− xCe xCuO 4

Abstract

Electrical resistance and magnetoresistance of the as-grown(x=0.160) and reduced(x=0.168) single crystals of Sm 2− x Ce x CuO 4 have been measured. The resistance of the as-grown sample with a current in the basal plane shows tendency toward localization below 90K. The magnetoresistance below 20K is negative and follows the log( H) law with the field parallel to the c-axis. Above 90K the resistivity of the as-grown sample is metallic. The magnetoresistance at 90K is positive and proportional to H 2 suggesting the band conduction. We find that the magnetoresistance at 4.2K and 90K is anisotropic and exhibits the largest relative change when the field is applied parallel to the c-axis. The anisotropy is associated with the 2- dimensional CuO plane structure. For the reduced superconducting sample themass anisotropy at 4.2K is determined to be about 1200 from the anisotropy of the resistive transition under the magnetic fields.