Microstructure and phonon vibration of the Fe-doped Bi2201 system

Polycrystalline samples of Bi1.8Pb0.2Sr2Cu1-xFexOy and Bi1.8Pb0.2Sr1.6+xLa0 .4-xCu1-xFexOy systems have been investigated by means of X-ray diffraction , electron diffraction, Raman scattering and resistivity measurements. It h as been found that Fe doping markedly influences the lattice parameters and decreases the monoclinic modulation wavelength. The frequencies of Oar pho non mode around 625 cm(-1) decrease by about 12 cm(-1) when Fe content incr eases from x = 0 to x = 0.5 for Bi1.8Pb0.2Sr2Cu1-xFexOy system, whereas for Bi(1.8)Pb(0.2)Sr(1.6+x)La(0.4-x)Ci(1-x)Fe(x)O(y), the frequencies of O-Sr mode are nearly unchanged with Fe doping. These results can be satisfactori ly interpreted by the "charge transfer" effect. The superconducting propert ies of both the systems are also discussed. (C) 2000 Elsevier Science B.V. All rights reserved.