Magnetisation and neutron diffraction studies of HoFe12-xTaxXy (0.5 <= x <= 0.7, X=H, C)

Magnetisation measurements, in particular the angular dependences of the co mponents of the magnetisation vector, parallel and perpendicular to the app lied field were measured on oriented powder samples of the HoFe11.4Ta0.6 al loy and its hydride and carbide. These experiments allow a study of the mag netocrystalline anisotropy and an accurate determination of the spin reorie ntation process occurring in the hydride. Moreover powder neutron diffracti on experiments led to a determination of the crystallographic and magnetic structures of these materials, in particular the values of the iron and hol mium moments on the different sites. Analysis of the results allows an esti mate of the magnetocrystalline anisotropy and of the exchange interactions. Accordingly their changes after hydrogen or carbon insertion in the starti ng alloy are determined. (C) 1999 Elsevier Science S.A. All rights reserved .