Effect of Cu(sup 2+) magnetic moments on the superconductivity of YBa2Cu3O7: The origin of the ''linear term'' in the specific heat; The volume fraction of superconductivity.

摘要

The concentration (n(sub 2)) of Cu(sup 2+) magnetic moments located on the YBa(sub 2)Cu(sub 3)O(sub 7) lattice is determined by the specific heat in a 7-T magnetic field. The discontinuity in specific heat at (Tc) ((Delta)C((Tc))) and also the coefficient of the linear term ((gamma)(0)) are correlated with n(sub 2) in a way that suggests the operation of a pair-breaking mechanism that limits the transition to the superconducting states and provides a criterion for the volume fraction of superconductivity. (gamma)(0) can be represented by the sum of two contributions, both associated with Cu(sup 2+) moments, implying that there is no contribution that is an intrinsic property of the superconducting state. The interpretation of the data provides estimates of parameters relevant to the recognition of strong-coupling effects. 12 refs., 5 figs. (ERA citation 15:032613)