FEATURES OF STRUCTURAL PHASE-TRANSITIONS IN CA2-XSMXMNO4

Features of structual transitions in Ca2-xSmxMnO4 have been investigat ed by means of electron diffraction. When the temperature is lowered f rom a high-temperature tetragonal (HTT) phase cn x = 0.3, there are su ccessive transitions from the HTT phase to a low-temperature orthorhom bic (LTO) one at 300 K and further to a low-temperature tetragonal (LT T) one at 100 K. In electron diffraction patterns, satellite spots wit h (q) over right arrow = 1/8[110] also appear below about 290 K. Featu res of the satellite spot are that it is observed in 0.1 less than or equal to x less than or equal to 0.35 and its location depends on x.