X-ray diffraction study on YBa_2Cu_3O_7/PrBa_2Cu_3O_7 superlattices with thinner YBCO layers

摘要

With the development of the technique of preparing thin film, artificial superlattices of high-T_c oxides, especially (YBa_2Cu_3O_7)_n/(PrBa_2Cu_3O_7)_m, have attracted much attention due to the possibilities of studying a variety of superconducting physical properties otherwise inaccessible, One of the many interesting characteristics of this system is the reduction of T_c with increase of the thickness of the PrBCO layer in superlattices with thin YBCO layer, which has been observed by many groups.Several theoretical models have been proposed to account for this interesting phenomenon, including a spin polaron model, Kosterlitz-Thouless transition, and proximity effect, but all of them do assume that the superlattices are of perfect multilayer structure, and ignore possible disorders at the interface, including the interdiffusion, step disorder and strain, etc. Here we report in detail some results on X-ray diffraction of a series of superlattice (YBCO)_n/ (PrBCO) _m with modulation ratio n:m, 1