MODIFICATION OF NORMAL-STATE AND SUPERCONDUCTING PROPERTIES OF HIGH-Tc OXIDES VIA TREATMENT BY METAL-PHTHALOCYANINES

Abstract

Exposure of Bi- or Tl-based high-T c oxide powders to vapors of metal-phthalocyanines MPc (M is Zn or Ni) resulted in the formation of a family of new compounds with modified crystal lattice parameters, electronic structure, phonon spectrum and magnetic properties as compared to the starting materials. Based on the combined X ray diffraction, scanning tunneling microscopy, optical, FT–IR and microwave absorption data, a model of crystal structure is proposed where the key feature is intercalation of MPc molecules between the Bi-O (Tl-O) bilayers. Values of dc magnetization at 300 K varied over two orders of magnitude as a function of chemical composition and nature of the central metal ion in MPc. Measurements of temperature dependence of magnetization of the intercalated samples revealed a divergence at low temperatures between the zero-field and the field-cooled cycles, though of lower magnitude as compared to the starting high-T c oxides. The results of this study suggest that treatment by MPc offers a possibility of controllable variation of key properties of high-T c oxides.