COMPTON-SCATTERING STUDY OF 4F MAGNETISM IN CEFE2

Magnetic Compton scattering, which measures solely the electron spin m oment, has been used to provide direct evidence for the low value of t he 4f moment on cerium in the ferrimagnetic compound CeFe2. The measur ements were performed by using monochromatic, 61.34 keV photons with a high degree of circular polarization produced by an elliptical multip ole wiggler at the Accumulation Ring Source, KEK, Japan, Analysis of t he Compton profile shows the 4f spin moment to be antiparallel to the moment on Fe, This is consistent with the 4f moment as deduced from ne utron-diffraction data yet conflicts markedly with the moment predicte d in a series of nb initio band calculations, being less than half the calculated value of 0.42 mu(B).