Comparative Study of the Nernst–Ettingshausen Coefficient in the Normal Phase in the Y1 – xPrxBa2Cu3Oy and Y0.85 – xPrxCa0.15Ba2Cu3Oy Systems

Abstract

The results of the comparative study of the modification of the temperature dependences of the Nernst–Ettingshausen coefficient Q in the normal phase of two series of the samples of the Y_1 – xPr_xBa₂Cu₃O_y and Y_0.85 – xPr_xCa_0.15Ba₂Cu₃O_y compositions due to praseodymium doping are presented. The specific features of dependences Q(T) and Q_300 K(T) appeared as additional calcium ions exist in the YBa₂Cu₃O_y lattice have been revealed and analyzed. It is shown that dependences Q(T) and the temperature dependences of the thermopower coefficient obtained for the same samples previously are completely described in terms of the narrow-band model for both systems under study. The charge carrier mobilities and the degrees of asymmetry of the dispersion law are determined using a quantitative analysis of the experimental data. It is shown that the existence of additional calcium ions in the lattice does not influence a change in the asymmetry of the dispersion law with an increase in the praseodymium content, but strongly influences the character of changing the mobility. The found dependence of the mobility on the level of doping in the two systems and the observed difference in the characters of the changes in the absolute values of the thermopower coefficient and the Nernst–Ettingshausen coefficient in the Y_0.85 – xPr_xCa_0.15Ba₂Cu₃O_y system are explained on the basis of the analysis of the mechanisms of influence of the energy spectrum parameters on the charge carrier mobility in the YBa₂Cu₃O_y system.