Hall and thermoelectric-power coefficients of superconductingNd2CuO4−xFx

Abstract

Both the Hall coefficient (${\mathit{R}}_{\mathit{H}}$) and the thermoelectric-power coefficient (S) have been measured using the same polycrystalline samples of superconducting ${\mathrm{Nd}}_2$ ${\mathrm{CuO}}_{4\mathrm{-}\mathit{x}}$ ${\mathrm{F}}_{\mathit{x}}$ (0≤x≤0.3). For the samples with 0.1≤x≤0.3, the ${\mathit{R}}_{\mathit{H}}$ of every sample is found to be negative in the temperature range between 30 and 275 K. Furthermore, as x increases, the charge-carrier density (${\mathit{p}}_{\mathit{H}}$) estimated from ${\mathit{R}}_{\mathit{H}}$ at 100 K increases in proportion to x (${\mathit{p}}_{\mathit{H}}$=x) up to around 0.18, then much more rapidly for x≥0.18. On the other hand, the S of every sample is also found to be negative in the temperature range between 30 and 300 K. The absolute value of S is found to reduce with x up to around 0.18 and then level off to a constant value as x increases further to 0.3. The decrease in ‖S‖ due to F doping is discussed using a semiconductor model. In addition, we point out a possibility that a magnon drag plays a significant role in S for samples with x