Relation of Tc with Hole Concentration in Ln1+xBa2-xCu3O7-δ (Ln=Sm and Eu); Hall Effect Measurement and Chemical Analysis

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Abstract
Hole concentration is investigated in single-phase samples of Ln1+x Ba2-x Cu3O7-δ (Ln=Sm and Eu) by two different methods: Hall effect measurement and iodometric titration. For both systems, the temperature dependence and x dependence of the effective hole concentration p H (=1/R H e) deduced from the Hall coefficient R H show behaviors very similar to those in Nd1+x Ba2-x Cu3O7-δ, which were reported previously. The superconductivity transition temperature T c shows a simple relation to p H deduced from R H just above T c, which is almost the same as that of the Nd-system. The hole concentration in a CuO2 sheet estimated from the chemical analysis yields almost the same value for p H, at least for samples with T c's lower than 70∼80 K. Thus, the relation of T c with hole concentration is essentially the same for three different compound systems Ln1+x Ba2-x Cu3O7-δ (Ln=Nd, Sm and Eu). This indicates that the superconducting T c is determined uniquely by the hole concentration in a CuO2 sheet, and that high-T c superconductivity is not affected by the value of the magnetic moment at the Ba site.