Crystal electric field excitations in ferromagnetic CeTX compounds

A ferromagnetic ground state was identified for the compounds CeCuGe (T-C = 10 K), CeCuSi (T-C = 15 K) [F. Yang, et al., J. Appl. Phys. 69 (1991) 4705] and CeAuGe (T-C = 10 K) [R. Pottgen, J. Magn. Magn. Mater. 152 (1996) 196]. The observed saturation magnetic moment values at low temperatures for all three compounds are considerably less than the theoretically expected value g(j)J = 2.14 mu(B) for the free Ce3+ ion involving the entire six-fold J = 5/2 multiplet, and thus provide a first indication of partial lifting of the f-electron level degeneracy in these compounds. Specific heat data yield crystal electric field (CEF) excitation energies (Delta(Sch)) equivalent to 140 K for CeCuGe, 110 K for CeCuSi and 280 K for CeAuCe. To confirm the presence of CEF excitations directly, we have carried out inelastic neutron scattering (INS) measurements on all three compounds, using the HET spectrometer at ISIS Facility. Here, we present a detailed analysis of the INS spectra of CeCuSi on the basis of a CEF model and the detailed analysis of the INS of the other two compounds will be reported elsewhere. (C) 2009 Published by Elsevier B.V.