The critical current density in the layered superconductors with ferromagnetic nanorods

Highlights: • A model simulating a HTSC layer with ferromagnetic nanorods is proposed. • A nonlinear critical current dependence on radius of nanorod is demonstrated. • A qualitative explanation of such dependence is suggested. - Abstract: In this paper, we have calculated the dependence of critical current density j_c on the radius R and concentration of extended ferromagnetic defects in the system simulating a high-temperature superconductor (HTSC) layer. It was shown that at fixed volume concentration of ferromagnetic fraction the j_c (R) dependence, as against nonmagnetic defects, has one maximum or two maxima at certain magnetization values of ferromagnetic fraction. We found that these maxima are due to the interplay of two parameters: concentration and effective depth of potential wells of defects.