A. N. Ignatenkov

The interplay of superconductivity and localization in Nd2−xCexCuO4+δ single crystal films

The influence of nonstoichiometric disorder on the in-plane resistivity and SC-transition has been investigated for Nd{2-x}Ce{x}CuO{4+\delta} single crystal films (x=0.15 and 0.18). It is shown that with increasing of

Two-dimensional quantum interference contributions to the magnetoresistance of Nd2−xCexCuO4−δ single crystals

\delta

In-plane and out-of-plane temperature dependencies of the resistivity in single crystals and films of Nd2CuO4

the in-plane normal state resistivity increases (the mean free path diminishes) and SC-transition temperature decreases with essential broadening of the transition region. The observed evolution from homogeneous metallic (and superconducting) Nd{2-x}Ce{x}CuO{4+\delta} system to inhomogeneous dielectric one is described as Anderson-type disorder-induced transition in a two-dimensional electron system.Abstract The influence of nonstoichiometric disorder on the in-plane resistivity and SC-transition has been investigated for Nd2−xCexCuO4+δ single crystal films (x=0.15 and 0.18). It is shown that with increasing of δ the in-plane normal state resistivity increases (the mean free path diminishes) and SC-transition temperature decreases with essential broadening of the transition region. The observed evolution from homogeneous metallic (and superconducting) Nd2−xCexCuO4+δ system to inhomogeneous dielectric one is described as Anderson-type disorder-induced transition in a two-dimensional electron system.

Properties of the mixed and normal states induced by magnetic field in a Nd1.82Ce0.18CuO4−δ film

Two-dimensional (2D) weak localization effects at low temperatures T=0.2–4.2 K are investigated in a nonsuperconducting sample Nd1.88Ce0.12CuO4−δ and in the normal state of a superconducting sample Nd1.82Ce0.18CuO4−δ for B>Bc2≃3 T. The phase coherence time τφ (≃5×10−11 s at 1.9 K) and the effective thickness d of a conducting CuO2 layer (≃1.5 Å) are estimated by fitting the expressions from the 2D weak localization theory to the magnetoresistivity data for the normal-to-plane and in-plane magnetic fields. The estimated value of the parameter d ensures the condition of strong carrier confinement and justifies a model of almost decoupled 2D metallic sheets for the Nd2−xCexCuO4−δ single crystals.

Influence of magnetic field on the superconducting transition in a Nd1.82Ce0.18CuO4−δ film

The temperature dependencies of the in-plane ρ ab (T) and out-of-plane ρ c (T) resistivities of two groups of Nd 2 CuO 4 single crystals (films and bulk single crystals) was investigated in a temperature range 20-300 K. The effect of modified heated treatment and annealing conditions on transport properties of the pra-crystals Nd 2 CuO 4 was studied. It was found that nonstoichiometric disorder leads to different dependencies of the resistivity both ρ ab (T) and ρ c (T).

Transport and localization in Nd{sub 1.82}Ce{sub 0.18}CuO{sub 4-{delta}} film

Abstract The temperature and magnetic-field dependences of the resistivitiy ϱ and Hall effect R (j‖ab, B‖c) in a Nd 1.82 Ce 0.18 CuO 4−δ single crystal film (T c = 6 K) is investigated at temperatures 1.4 ≤ T ≤ 20 K and magnetic fields 0 ≤ B ≤ 5.5 T. The negative magnetoresistance (NM) due to the weak-localization effect in the normal state is observed for B > 3 T. The resistivity behavior and the inversion of the sign of R(B) in the mixed state are explained in a reasonable way by the flux-flow model with the effect of pinning taken into account.

Behaviour of both in-plane and out-of-plane resitivities of Nd2−xCexCuO4 single crystals

The temperature and magnetic-field dependences of the resistivity ρ and Hall effect R(j‖ab, B‖c) in a Nd1.82Ce0.18CuO4−δ single crystal film (Tc=6 K) is investigated at temperatures 1.4≤T≤20 K and magnetic fields 0≤B≤5.5 T. At the lowest temperature T=1.4 K the resistive state (exhibiting resistivity and the Hall effect) arises in a magnetic field B=0.5 T. A transition to the normal state is completed at Bc2≃3 T, where the Hall coefficient becomes nearly constant. The negative magnetoresistance due to the weak-localization effect in the normal state is observed for B>3 T. The nonmonotonic behavior and the inversion of the sign of R(B) in the mixed state are explained in a reasonable way by the flux-flow model with the effect of pinning taken into account.

Effect of nonstoichiometric disorder on the transport properties of Nd2−xCexCuO4+δ single crystal films☆

Temperature- and magnetic-field-dependences of the resistivity {rho} and Hall effect R{sub H}(j{parallel}ab, B{parallel}c) in Nd{sub 1.82}Ce{sub 0.18}CuO{sub 4{minus}{delta}} single crystal film (T{sub c} = 6 K) were investigated at temperatures 1.4 {le} T {le} 20K and magnetic fields 0 {le} B {le} 5.5 T. At the lowest temperature T = 1.4 K the resistive state and Hall effect appear at the same magnetic field B = 0.5 T. A transition to the normal state is completed at B{sub c2} {approx_equal} 3T when a Hall coefficient becomes almost invariable. The negative magnetoresistance (d{rho}/dB 3 T was observed also. The sign change of the temperature coefficient d{rho}/dT corresponds B = 1.06 T. This fact does not connect with transition in a new state but this is an accidental compensation of two factors: a decreasing of B{sub c2} with temperature and negative value d{rho}/dT in the normal state owing to weak localization effect.AbstractTemperature- and magnetic-field — dependences of the resistivity ϱ and Hall effect RH

minus;

(\vec j\parallel ab,\vec B\parallel c)