Vortex pinning and magnetic peak effect in Eu(Eu,Ba)_(2.125)Cu_3O_x

摘要

Eu-Ba-Cu-O composition was synthesized by solid state reaction technique. To determine optimum growth temperature, heat treatment was examined on the material at 880-1,100 ℃. Microstructural evolution, phase formation and elemental distribution depending on heat treatments were examined by using X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectroscope analysis. Optimum fabrication conditions were determined as 1,020 ℃ for 24 h under oxygen atmosphere and detailed characterization of corresponding compound was performed. The magnetization hysteresis loops are expounded to be the product of superconducting Eu-123 grains and magnetic Eu~(2＋) ions. The peak effect on the magnetization curves was described by the extended critical state model. Scaling of the pinning force was found such that the peak position is proportional to the irrevers-ibility field H_(irr) and the maximum pinning force is proportional to H_(irr)~2.