Polarised neutron diffraction measurements on CeFe2 and LuFe2

摘要

Polarised neutron diffraction measurements on polycrystalline CeFe2 and LuFe2, the end members of the rare-earth (R)-based RFe2 Laves phase compounds show, in both compounds, a clearly measurable flipping ratio, of less than unity, on the (2 2 0) Bragg peak whose structure factor involves the R sub-lattice only. The results are in good agreement with the earlier single crystal measurements on CeFe2 but supercede a similar single crystal study on LuFe2 that apparently did not detect a magnetic moment on the Lu site. Evaluation of the magnitude of the 5d moment from the flipping ratio on the (2 2 0) peak requires a large extrapolation to Q = 0, via an assumed form factor and hence is subject to large uncertainty. The observed 5d moment is, nevertheless, consistent with the results of X-ray magnetic circular dichroism (XMCD) measurements as well as theoretical predictions (-0.3mu(B)). In contrast, however, while the data on CeFe2 indicate a substantial 5d moment (> -0.7mu(B)) they appear inconsistent with the large 4f moment (with significant magnitudes for both orbital and spin components) predicted theoretically and also claimed to be observed in XMCD studies. (C) 2003 Elsevier B.V. All rights reserved. [References: 11]