A MAGNETIC, NEUTRON-DIFFRACTION, AND MOSSBAUER SPECTRAL STUDY OF THE TB2FE17-XGAX SOLID-SOLUTIONS, WITH 7-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-9

The compositional dependence of the Curie temperature of the Tb2Fe17-x Gax solid solutions shows a primary maximum for x equal to three and a secondary maximum for x equal to eight. The Mossbauer spectra and pow der neutron diffraction patterns of Tb2Fe9Ga8 indicate that gallium av oids the 9d site, completely fills the 6c site. and occupies preferent ially the 18f site over the 18h site. This gallium preferential substi tution leads to a nearly ordered two-dimensional antiferromagnetic arr angement of the terbium and iron magnetic moments, an increase in Curi e temperature, and a surprisingly sharp Mossbauer spectrum. (C) 1998 E lsevier Science B.V. All rights reserved.