Synthesis, structural and magnetic properties of the interstitial compounds RCo9Si2Cx with R = Sm, Nd, Y and O≤x≤1.8

The crystal structure and the magnetic properties of silicon substituted and carbon inserted R-Co based materials (R=Y, Nd, Sm) have been studied. Carbon insertion in the RCo9Si2 compounds decreases the Curie temperature and the magnetic moment mu(Co). In all the compounds, the anisotropy of the cobalt sublattice is planar whereas the second order crystal electric field acting on R favours a uniaxial or a planar anisotropy for rare earth elements with positive (Sm) or negative (Nd) sign of alpha(1) the second order Stevens' coefficient, respectively. Carbon insertion yields an increase of the 3d sublattice anisotropy, and probably of the R sublattice anisotropy. A comparison of the overall 3d magnetic properties is made with some R-Fe intermetallics where p-elements (C, N, Si) are alloyed. (C) 1998 Elsevier Science S.A. All rights reserved.