MODIFICATION OF NORMAL-STATE AND SUPERCONDUCTING PROPERTIES OF HIGH-T_c 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.

The chemical and adsorption effects of foreign molecules on the properties of high-temperature superconductors

“…In Ref. 252, as in previous studies, 250,251 unusual physical properties of these ceramics at room temperature were reported. For example, at 300 K the magnetisation of a metal phthalocyanine intercalated in the ceramics was found to be anomalously high, two orders of magnitude higher than the magnetisation of a free metal phthalocyanine complex.…”

“…High magnetisation of intercalated bismuth-and thallium-containing HTSC oxides can also be due to the joint orbital contribution of p-electrons of aromatic molecules, which can form two-dimensional conducting layers due to the structural features of the material. According to X-ray diffraction data, 252 intercalation changes the material structure substantially. Not only do the distances between the structural Tl7O and Bi7O layers change, but also those between the atoms along the a and b axes (see Fig.…”

“…The effect of the amount of the metal phthalocyanine intercalated in the ceramics on this process was observed for the (NiPc) y Bi 2 Sr 2 CaCu 2 O z system. 252 V. The effect of superconductivity on the electronic state of the adsorbed molecules and on adsorption processes…”

Intercalation of cationic phthalocyanines into layered titanates and control of the microstructuresElectronic supplementary information (ESI) available: CHN analytical data and amounts of PA and Pc intercalated in Ti3O7 (Table S1), and XRD patterns of products derived from H2Ti3O7 (Fig. S1). See http://www.rsc.org/suppdata/jm/b2/b210237b/

“…13 In particular, immobilization of dyes and formation of their aggregated states are of importance for controlling the properties of materials, such as the photosensitization of TiO 2 14 and the photoconductivity of the aggregates. 15 Although intercalation of phthalocyanines into layered materials has been investigated using clays, layered double hydroxides, layered perovskites, and so on, [16][17][18][19][20][21][22] only the formation of dimers in the galleries [16][17][18] has been investigated and there have been no studies on the formation of aggregates.…”

Large positive magnetoresistance and transport properties of intercalated Cu oxides

“…High-temperature superconducting Cu oxides have a layered crystal structure and some of them, such as BiSCCO (Bi 2 Sr 2 Ca n−1 Cu n O 2n+4 , where n = 1, 2 or 3 is the number of Cu-O layers in the unit cell) can be intercalated with various atomic and molecular species bringing about a dramatic modification of the superconducting and normal-state properties [2][3][4][5][6]. In particular, intercalation of the BiSCCO n = 2 with metal phthalocyanines, MPc (where M is Fe or Ni, and Pc is C 32 H 16 N 8 ) has been shown to give rise to two new crystal structures with the c-axis expanded by 0.305 or 0.431 nm in (MPc) x BiSCCO with x = 0.05 or 0.1, respectively [4] (figure 1).…”