Low-energy and crystal field excitations in single- crystalline CeCu
2Ge
2in fields up to 12 T
M. Loewenhaupt
1, A. Schneidewind
2, E. Faulhaber
3and O. Stockert
41
IFP, TU Dresden
2
Helmholtz-Zentrum Berlin, PANDA group
3
Helmholtz-Zentrum Berlin, PANDA group
4
MPI-CPfS
E-Mail: loewenhaupt@physik.tu-dresden.de
CeCu2Ge2 is a magnetically ordered (TN = 4.1 K) Kondo lattice with a moderate enhanced Sommerfeld coefficient of 140 mJ/molK2. We performed inelastic neutron scattering experiments on a 2 g single crystal of CeCu2Ge2 using the cold triple-axis spectrometer PANDA at FRM II covering the low-energy “magnon”-range below 2 meV up to the crystal field excitations at around 18 meV [1]. Data were taken between 0.5 K and 10 K and in magnetic fields up to 12 T applied perpendicular to the (110/001) scattering plane. At zero field the low-energy magnetic excitations show an energy gap of 0.5 meV at all investigated Gamma points in the (110/001) plane with similar intensities. Away from the Gamma points the magnetic excitations become dispersive merging into a band of excitations around 1 meV.
For increasing magnetic fields the gap energy decreases indicating opposite action of external and internal magnetic fields. Concomitant the crystal field excitations broaden and decrease slightly in average energy. The results will be discussed in the framework of local, crystal field related, and non-local, spin-wave-like, magnetic excitations. The possibility of a quantum phase transition at 8 T [2] is also discussed.
References
[1] M. Loewenhaupt et al., J. Appl. Phys. 111, 07E124 (2012) [2] D. K. Singh et al., Sci. Rep. 1, 117 (2011)
