X-ray diffraction, Raman, infrared and Mössbauer spectra of heavily Fe doped Bi₂Sr₂Ca₁Cu₂O_8+d

Abstract

We report measurements on x-rays diffraction and Raman, infrared and Mössbauer absorption spectra of Bi₂Sr₂Ca₁(Cu_1−x, Fe_x)₂O_8+δ, 0·05≤x≤0·25. X-ray analysis shows that the increment of Fe in the CuO₂ layers results in the growing of the n=1 phase at the expense of the n=2, with possible segregation of Fe at the higher dopant concentration. Mössbauer characterization requires two different configurations for the Fe in the n=2 phase. Only one doublet is assigned to the Fe at the Cu site for n=1. The resulting spin configuration shows an one mode behavior for the 2-magnon Raman response. These low temperature normal state spectra have resonant behavior that help to put in evidence a second weaker band at higher frequencies, assigned to four spin exchanges. Infrared spectra, in agreement with isomer shifts suggesting the presence of Fe³⁺, yields ionic features expected for an environment with long range interactions in which oxygen ions play a main role.