High-energy neutron scattering from heavy-fermion systems Ce(In 1− xSn x) 3 and Ce(Pt 1− xRh x) 2

Abstract

We report neutron-scattering measurements on the heavy-Fermion systems Ce(In 1− x Sn x ) 3 and Ce(Pt 1− x Rh x ) 2. For x = 0, the pure compounds CeIn 3 and CePt 2 order antiferromagnetically at 10.2 and 1.7 K, respectively. Above these temperatures, in the paramagnetic phase, they show a quasi-elastic central ‘peak’ as well as a crystal-field excitation Γ 7 → Γ 8. As x increases the crystal-field excitation becomes ‘quenched’ in both systems and the ground-state ( 2 F 5 2 ) response degenerates into a single broad Lorentzian hump centered on a characteristic energy which increases progressively to a value of ∼ 35 meV for CeSn 3 and as high as ∼ 115 meV for CeRh 2. In the series of compounds Ce(In 1− x Sn x ) 3 the spin-orbit excitation 2 F 5 2 → 2 F 7 2 is found to shift progressively to higher energies with increasing x. The increase with x above the free-ion value of ∼ 273 meV is at a rate roughly twice the characteristic energy of the ground manifold. This implies that the characteristic energy of the 2 F 7 2 state is roughly twice that for the 2 F 5 2 state. Similar enhancements of the spin-orbit excitations in the system Ce(Pt 1− x Rh x ) 2 are expected.