Equilibrium magnetic characteristics of high-T[sub c] superconductors with allowance for the spatial distribution of the order parameter in the vortex cores. I. Equilibrium magnetization.

An investigation is made into the accuracy of the theoretical description of the field dependence of the equilibrium magnetization M(H) of type-II superconductors with Ginzburg-Landau parameters κ>1 in various approximations for magnetic fields H much less than the upper critical field H[sub c2]. It is found that taking the spatial distribution of the order parameter into account has a substantial effect on the behavior of the magnetization M(H) even at the very lowest fields in the close vicinity of the lower critical field H[sub c1]. The mechanisms through which and the degree to which the field dependence M(H) is influenced by such factors as the self-energy of the vortex, the accuracy of description of the spatial distribution of the vortex field, the suppression of the order parameter due to the overlapping of the vortices, and the use of the principle of superposition of fields are investigated for fields in the interval H[sub c1]≼H«H[sub c2]. In this field interval an analytical expression for M(H) is obtained by direct evaluation of the lattice sums with allowance for the influence of the structure of the vortex cores. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]