A POLARIZED NEUTRON STUDY OF THE MAGNETIC FORM-FACTORS IN CEFE2

The magnetization distribution in the ferromagnetic phase of CeFe2 at 10 K has been determined using a combination of polarized and unpolarized neutron diffraction measurements on a single crystal. The results confirm previous results on powders, and the prediction of band structure calculations, that both the Fe and Ce atoms carry a magnetic moment, and that Ce is magnetized oppositely to Fe. The value of the Fe moment deduced from the measurements is mu(Fe) = 1.174(10) mu(B), somewhat smaller than that given by the theory. The value obtained for the Ce moment is strongly dependent on the assumption made about the relative numbers of unpaired 5d and 4f electrons. If the ratio of 5d/4f magnetization is taken as the value obtained in the band structure calculations (i.e. 0.75) the total Ce moment is -0.14(3) mu(B). The magnetization distribution around the Fe atoms deviates significantly from spherical symmetry; the form of the asymmetry indicates that the electrons occupy orbitals which are a coherent mixture of E(g)-like and T2g-like functions.