Equilibrium magnetic characteristics of HTSC with regard to spatial distribution of the order parameter in vortex cores'. I. Equilibrium magnetization

The problem of accuracy of theoretical description of the field dependences of equilibrium magnetization M(H) in high-k type-II superconductors, calculated in different approximations, is studied for low magnetic fields H<<Hc2. It is shown that account of spatial distribution of the order parameter influences essentially the behavior of magnetization M(H). We investigate the mechanisms and the effect on the magnetization of such factors as the energy arising from the depression of the order parameter in the vortex core, the accuracy of the description of the spatial distribution of the vortex field, the depression of the order parameter due to the overlapping of vortices and the use of the principle of linear superposition of fields. A analytical expression for the dependence M(H) is obtained by straightforward calculation of the lattice sums, taking into account the effect of the vortex core structures for the field region Hc1≤H<<Hc2