Anomalies of conductivity behavior near the paramagnetic-antiferromagnetic transition in single-crystals La2CuO4+delta

作者：Belevtsev B I^*; Dalakova N V; Panfilov A S; Beliayev E Yu

来源：Physica B: Condensed Matter , 2010, 405(5): 1307-1311.

DOI：10.1016/j.physb.2009.11.074

• Cuprates
• Paramagnetic-antiferromagnetic transition
• Phase separation
• Superconductivity

The temperature dependences of resistance, R(T), of two single-crystals La2CuO4+delta samples have been studied with the aim to detect a possible change in the R(T) behavior induced by paramagnetic-antiferromagnetic (PM-AFM) transition. One of the samples with delta less than or similar to 0.01, was fairly homogeneous in oxygen distribution (not phase-separated) with Neel temperature T-N approximate to 266 K. Conductivity of this sample has been determined by Mott's variable-range hopping below T-N. The other, far less resistive, sample with delta approximate to 0.05, was inhomogeneous (phase-separated) showing both PM-AFM (T-N approximate to 205 K) and superconducting (T-c approximate to 25 K) transitions. It is found that for the homogeneous sample the resistivity decreases above T-N far faster with temperature than below it (for both directions of measuring current, parallel and perpendicular to basal CuO2 planes). A similar behavior of conductivity near PM-AFM transition is also found for the phase-separated and less resistive sample. in this case a clear kink in R(T) curve near T-N approximate to 205 K can be seen. Furthermore, a transition to metallic (dR/dT > 0) behavior occurs far enough above T-N. The observed behavior of the samples studied is related to increased delocalization of charge carriers above T-N. This is in accordance with decrease in the AFM correlation length and corresponding enhancement of the hole mobility above T-N known for low-doped lanthanum cuprates.

• 出版日期2010-3-1