Structure and magnetic properties of Y2Co17-xSix compounds

The Y2Co17-xSix compounds have the hexagonal Th2Ni17 structure for x = 0 bu t the rhombohedral Th2Zn17 structure for 0.1 less than or equal to x less t han or equal to 2. Both structure types co-exist for higher Si concentratio ns (x = 3). The compounds with 0 less than or equal to x less than or equal to 1 have an easy magnetisation direction perpendicular to the c-axis at r oom temperature, but parallel to the c-axis for 1 < x less than or equal to 3. The Co moment and the Curie temperature decrease strongly with increasi ng Si concentration. We also determined the values of the anisotropy consta nt K-1 which change from negative to positive around x = 0.7. This behaviou r is discussed in terms of preferential Si substitution. (C) 1999 Elsevier Science B.V. All rights reserved.