Crystal field excitations in CeCu 2 Ge 2 : Revisited employing a single crystal and inelastic neutron scattering

• Published in: Journal of applied physics 2012-02, Vol.111 (7), p.07E124-07E124-3
• Main Authors: Loewenhaupt, Michael, Faulhaber, Enrico, Schneidewind, Astrid, Deppe, Micha, Hradil, Klaudia
• Format: Article
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.3673816

The intermetallic compound, CeCu 2 Ge 2 , is the counterpart of the heavy-fermion superconductor CeCu 2 Si 2 . CeCu 2 Ge 2 is a magnetically ordering ( T N =4.1K) Kondo lattice with a moderate Sommerfeld coefficient of 140 mJ/ mol K 2 . Earlier inelastic neutron measurements on a polycrystalline sample revealed a doublet ground state and a quasi-quartet excited state at 16.5 meV, although a splitting of the 4 f 1 (J=5/2) ground state multiplet into 3 doublets is expected from the point symmetry of the Ce 3 + ions. We performed detailed inelastic neutron scattering experiments on a single crystal at the thermal triple-axis spectrometer PUMA at FRM II for different crystallographic directions. From our results we infer that the quasi-quartet, in fact, consists of two doublets at 17.0 and 18.3 meV which exhibit a strong directional dependence of their transition matrix elements to the ground state doublet. Finally, we will present a new set of crystal field parameters.