SPECIFIC HEAT OF THE HIGH-Tc SUPERCONDUCTORS (La, M)2CuO4 AND YBa2Cu3O7 IN MAGNETIC FIELDS

Abstract

The specific heats, C, of the high-Tc superconductors YBa2Cu3O7, La1.85Ca0.15CuO4 and La1.85Sr0.15CuO4 have been measured from 0.4 K to above the superconducting transition temperature in magnetic fields, H, from 0 to 7 T. From measured changes in C with H, values of γ(H) = [C(H)/T]T=0 and γC/Tc = [(CS– Cn)/T]T=Tc have been evaluated. These results have been used to estimate the normal state y, the fraction of the sample that is superconducting in zero field, fs, and the value of the upper critical field, [Hc2]T=0.