MAGNETIC-PROPERTIES OF LA2NIO4.16 AND LA2-XPRXNIO4+DELTA

Magnetic properties of La2NiO4.16 and La2-xPrxNiO4+delta are studied b y dc susceptibility in a wide temperature range, i.e., 4-1200 K, The p rincipal aim is to investigate the modifications of magnetic interacti ons in the NiO2 plane bg inserting a magnetic ion in the LaO layer. Ma gnetic properties are considerably different with and without praseody mium. When 0 < x less than or equal to 2 the solid solution follows th e Curie-Weiss law and the Curie constant varies linearly with x, For x = 0, the susceptibility is smaller and another contribution appears a bove 200 K that is treated as the result of clusters of AF-coupled spi res of two-dimensional character. Our model ffts very well the data fr om 4 to 1000 It. Comparing the Curie-Weiss temperature with and withou t Pr suggests that small Pr quantities modify the in-plane Ni-O-Ni mag netic interactions and, thus, decrease the Curie-Weiss temperature. We think this is not a structural effect; it might correlate with an inc reased resistivity when Pr is substituted, Far larger substitution, i, e., x > 0.5, a single Pr3+ effect might dominate. (C) 1998 Academic Pr ess.