| Popis: |
The specific heats, C , of the high- T c superconductors YBa 2 Cu 3 O 7 , La 1.85 Ca 0.15 CuO 4 and La 1.85 Sr 0.15 CuO 4 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 Δ C / T c = [( C s − C n )/ T ] T = T c have been evaluated. These results have been used to estimated the normal state γ, the fraction of the sample that is superconducting in zero field, | s , and the value of the upper critical field, [ H c2 ] T =0 . |
