Magnetic neutron scattering and crystal-field states in CeCu2Si2

Abstract

The energy-loss spectra of Ce${\mathrm{Cu}}_2$ ${\mathrm{Si}}_2$ and La${\mathrm{Cu}}_2$ ${\mathrm{Si}}_2$ have been determined using neutrons of high incident energy. The magnetic part of the low-temperature spectra of Ce${\mathrm{Cu}}_2$ ${\mathrm{Si}}_2$ consists of a quasielastic line and two inelastic lines at 12.5 and 31 meV resulting from transitions between the Kramers ground state and two excited crystal-field doublets of ${\mathrm{Ce}}^{3+}$ in tetragonal symmetry. When positions as well as intensities of the inelastic lines are used, the crystal-field level scheme can be derived. The temperature dependence and magnitude of the quasielastic linewidth suggest that the contribution of Kondo-type spin fluctuations to the spin dynamics of Ce${\mathrm{Cu}}_2$ ${\mathrm{Si}}_2$ predominates over that of valence fluctuations. No indication of any magnetic ordering in Ce${\mathrm{Cu}}_2$ ${\mathrm{Si}}_2$ was found by neutron diffraction down to the mK range.