Specific Heat Linear Term in YBa2Cu3O7−x and a Survey of Related Compounds

Abstract

We have measured the specific heat, C, in the temperature range 0.3 to 20K and in magnetic fields up to 12 Tesla of several compounds related to the high-T_c superconductors. The linear term in C for YBa₂Cu₃O_7−x is only weakly dependent on oxygen concentration in the range 0 ≤ × ≤ 0.7. The linear term in C changes by less than 10% at 10 Tesla for La_1.98Sr_.02CuO₄, whereas for YBa₂Cu₃O_7−x it is obscured by additional field-dependent structure. Magnetic ordering anomalies are observed in YBa₂Cu₂O₅ at 10.6 K and in BaCuO₂₊₆ at 9.3 K.