MOSSBAUER STUDY OF MODULATED STRUCTURE OF BI2SR2CAFE2OY PHASE

Fe-57 Mossbauer studies of the single crystals of the Bi2Sr2CaFe2Oy co mpound with modulated structure show two quadrupole-splitting doublets (QS(1) = 1.03 mm/s and QS(2) = 0.45 mm/s). The compound is weak param agnet in the temperature range 330 K - 4.2 K. Analysis of the obtained data shows that the Fe atoms in this structure are separated into two groups, which can be attributed to small and strong distorted environ ments of the Fe atoms. They are in the Fe3+ valence state. An attempt is made to relate the feature of the results with the structure modula tion. From the full profile analysis of the X-ray diffraction data it follows that the modulation wave can be described by a spectral profil e dose to a ''rectangular'' one. In the obtained domain-like system th e Fe atoms can be divided into two unequal groups having opposite dire ctions of displacements in good agreement with Mossbauer data.