ANTIFERROMAGNETIC INTERACTIONS AND MOSSBAUER STUDY OF LNMCUFEO(5+DELTA) PHASES (LN=Y,LA, M=CA,SR,BA)

A three-dimensional antiferromagnetic ordering 3D-AF at T-N approximat e to 12 K has been observed in these nonsuperconducting phases. In the compounds where a partial trivalent-divalent cationic substitution (Y by Ca or La by Sr) has been performed, this antiferromagnetic orderin g is not observed above 4 K. Mossbauer spectroscopy studies indicate a unique iron environment and magnetic ordering; the spectra are consis tent with the classic high spin Fe3+ although in an unusual fivefold c oordination. Both the herein described transition and the formerly rep orted one at similar to 460 K are affected upon doping.