MAGNETIC-PROPERTIES OF R2BANIO5 OXIDES

The magnetic behaviour of the R2BaNiO5 (R=Rare Earth or Y) family of o xides has been characterized by means of neutron diffraction and magne tization measurements. These compounds present strong one-dimensional antiferromagnetic (1D-AF) fluctuations along the octahedra (NiO6) chai ns, parallel to the crystallographic a-axis. Without direct oxygen lin ks between chains, the magnetization data for Y2BaNiO5 show a broad ma ximum caused by the 1D-AF fluctuations. Two anomalies in the susceptib ility have been observed in the compounds with R magnetic, which are a ssociated with the 3D magnetic ordering of Ni and rare earth sublattic es, separately. The magnetic field dependence of the magnetization at low temperature reveals field induced transitions in most of these com pounds.