Specific heat of GdBa2Cu3O7−δ in the normal and superconducting states

Abstract

The specific heat c, resistance R, and magnetic susceptibility χ of the high-temperature superconductor GdBa2Cu3O7−δ have been measured from 1.5 to 180 K and compared with those of YBa2Cu3O7−δ and La1.85Ba0.15CuO4. For the Gd compound, an antiferromagnetic transition is seen in the specific-heat data at 2.24 K, and a Curie-Weiss dependence of χ is also seen, with 7.98μB per Gd ion and 1χ extrapolating to zero at -5.89 K. The entropy associated with this peak in the specific heat is consistent with an assignment of J=72 to the total angular-momentum quantum number of the Gd ion, indicating that crystal-field effects are small. The specific heat of the Gd compound is larger than that of the Y compound at these temperatures; this is attributed to the larger mass of the Gd ion. A peak in cT3 near 20 K in the Gd compound indicates a sharply defined peak in the phonon density of states near 10 meV. The superconducting transition temperature Tc of GdBa2Cu3O7−δ indicated by the specific-heat data is 93.8 K, and the jump in the specific heat at Tc is 301 mJ/K g-atom, in agreement with previous observations for YBa2Cu3O7−δ. Evidence is seen for a temperature-dependent phonon density of states in GdBa2Cu3O7−δ, and it is pointed out that such a temperature dependence is also seen in previously published data for La1.85Ba0.15CuO4 and La1.8Sr0.2CuO4.

Source-reported materials — not catalogue approval

Similar papers