DEVIATION FROM THE STOICHIOMETRIC COMPOSITION OF SINGLE-CRYSTAL ER2CO17

The deviation from the stoichiometric composition of single-crystal 'E r2Co17' has been determined by theoretical analysis. It is found that the composition of this single-crystal 'Er2Co17' is rich in cobalt, an d its real composition is suggested to be Er2-deltaCo17+2 delta (delta = 0.14) on the basis of a comparison of calculations based on the sin gle-ion model with a series of experiments. The values of the Er-Co ex change field H-ex and the crystalline-electric-field (CEF) parameters A(n)(m) at the rare-earth (R) site in the 'Er2Co17' compound are also evaluated at the same time. The experiments provide the following data : the temperature dependence of the spontaneous magnetization of the c ompounds and the normalized magnetic moment of the Er ion, the magneti zation curves dong the crystallographic axes at 4.2 K and 200 K, and t he temperature dependence of the magnetization along the crystallograp hic axes in a field of 4 T.