Preferential cobalt site occupation in some R(3)(Co, M)(11)B-4 compounds

Structural and magnetocrystalline anisotropy results obtained by X-ray diffraction on random and magnetically aligned powder samples of Y(3)Co(11-x)M(x)B(4) with M = Fe or Al, Gd3Co11-xNixB4 and Er3Co11-xAlxB4 are presented. It is found that compounds with the Ce3Co11B4-type structure are formed for iron or nickel contents of x less than or equal to 6 and for an aluminium content of x less than or equal to 3. The diffraction patterns of magnetically aligned powders show that Y(3)Co(11-x)M(x)B(4) With M = Fe or Al change from easy c-axis to easy-plane anisotropy for x less than or equal to 1. In contrast, Gd3CO11-xNixB4 and Er3Co11-xAlxB4 remain uniaxial in the studied composition ranges. Based on structural and magnetic data and under the assumptions of the model of individual site contribution to anisotropy (ISA), preferential occupations by Fe and Al of the Co(2c) sites and by Ni of the Co(3g) sites are inferred. (C) 1997 Elsevier Science Ltd.