We present the investigation results of the in-plane ρ(T) resistivity tensor at the temperature range 0.4-40 K in magnetic fields up to 90kOe (H c, J ab) for electrondoped Nd 2−x Ce x CuO 4+δ with different degree of disorder near antiferromagneticsuperconducting phase boundary. We have experimentally found that for optimally doped compound both the upper critical field slope and the critical temperature decrease with increasing of the disorder parameter (d-wave pairing) while in the case of the underdoped system the critical temperature remains constant and (dH c2 /dT )| Tc increases with increasing of the disorder (s-wave pairing). These features suggest a possible implementation of the complex mixture state as the (s+id)-pairing.

The magnetic-field dependencies of the longitudinal and Hall resistance of the electron-doped compounds Nd 2−x Ce x CuO 4+δ in underdoped region with x = 0.14 and with varying degrees of disorder (δ) were investigated. It was established experimentally that the correlation between the longitudinal electrical resistivity and the Hall resistivity can be analyzed on the basis of scaling relationships: ρ xy (B)∼ ρ β xx (B). For the totality of the investigated single-crystal films of Nd 2−x Ce x CuO 4+δ /SrTiO 3 the universal value β = 1.5 ±0.4 is found. The observed feature in the electron-doped two-dimensional systems can be associated both with a displaying of anisotropic s -wave or d-wave pairing symmetry and with a rather strong pinning due to an essential degree of disorder in the samples under study.

The magnetic-field dependencies of the longitudinal and Hall resistivity of the electron-doped compounds Nd2–xCexCuO4+δ in underdoped region (x = 0.14) were investigated. It was established experimentally a strong magnetic field dependence of the Hall conductivity, σxy(B) = C – b/B, in the region of magnetic fields corresponding to a transition from superconducting to resistive state. The observed feature can be explained with the sum of contributions of the quasiparticles and moving Abrikosov vortices into Hall effect in a mixed state of type-II superconductor.

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We report on the results of analyzing the temperature dependences of the resistivity of the Nd 2 ⎯ x Ce x CuO 4 + δ electronic superconductor with x = 0.14 (underdoped range), x = 0.15 (optimal doping), and x = 0.18 (overdoped range) and with various degrees of annealing in an oxygen free atmosphere in mag netic fields up to H = 90 kOe (H || c, J || ab) in the temperature range T = (0.4-300) K. It is shown that the observed differences in the dependences of the slope of the upper critical field on the degree of disorder in the Nd 2 -x Ce x CuO 4 + δ system upon a change in the cerium doping level indicate a change in the symmetry of d type pairing to anisotropic s pairing.