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H. Michor, D.T. Adroja:
"Inelastic Neutron Scattering Study of the Crystalline Electric Field of CeNi₉GeGa₃ and CeNi₉Ga₄";
Bericht für ISIS, Rutherford Appleton Laboratory; Berichts-Nr. RB 1810773, 2019; 3 S.

A current hot topic in correlated electron physics is the magnetic phase diagram resulting from competing Kondo and RKKY interactions with magnetic frustration. One interesting system in this context is CeNi₉Ga₄ and solid solutions CeNi₉Ge_4-xGa_x which crystallizes in a tetragonal structure (derivative of the cubic NaZn₁₃-type).
CeNi₉Ga₄ exhibits a paramagnetic ground state with a huge Sommerfeld coefficient γ exceeding 5.5 J/molK² and, via substitution, was found to be near a heavy fermion quantum critical point. The latter appears being stabilized by a quasi-quartet crystal field (CEF) ground state degeneracy of CeNi₉Ga₄. In the solid solution series CeNi₉Ge_4-xGa_x a pronounced weakening of the Kondo interaction is observed and the appearance of long range magnetic order with a maximum T_N ~2.8 K for CeNi₉Ge₃Ga. The objective of the present experiment is to investigate crystal field excitations in two compounds, CeNi₉Ga₄ and CeNi₉GeGa₃ by inelastic neutron scattering in order to understand the complex magnetic ground state. LaNi₉Ga₄ and LaNi₉GeGa₃ serve as 4f⁰ reference samples for the evaluation of the inelastic phonon background contributions.