SPIN-GLASS BEHAVIOR IN SR3FERUO7 AND SR4FERUO8

The crystal structure of the new Ruddlesden-Popper phase Sr3FeRuO7 has been refined from neutron powder diffraction data collected at 1.7 K; space group I4mmm, a = 3.9187(1), c = 20.4146(3)Å. The crystal structure of the K2NiF4-like compound Sr4FeRuO8 has also been refined; space group I4mmm, a = 3.9025(1), c = 12.5943(3)Å. Neither compound appears to be magnetically ordered at 1.7 K. However, the magnetic susceptibilities of Sr3FeRuO7 and Sr4FeRuO8 have maxima at 23 K and 11 K, respectively, and show hysteresis effects below these temperatures. This behavior is interpreted in terms of magnetic frustration arising from the presence of competing superexchange interactions between Fe3+ and Ru5+ cations in nearest-neighbor and next-nearest-neighbor sites. © 1992 Academic Press, Inc.