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Orbital dependent magnetic exchange interaction in CeX$_{\text{c}}$ (X$_{\text{c}}$=S, Se, Te)

Dispersion relations of the crystal-field excitations in cubic antiferromagnets CeTe, CeSe, and CeS have been investigated by inelastic neutron scattering using single crystalline samples. The Fourier transform of the magnetic exchange interaction $J(q)$ obtained from the crystal-field dispersion is largely different from that of the mean-field interaction obtained from the Néel temperature and the Weiss temperature. From detailed reexamination of the magnetic susceptibility and these $J(q)$ relations, we conclude that the magnetic exchange interaction is dependent on the crystal-field levels. The interaction associated with the $Γ_8$ excited state is stronger than that with the $Γ_7$ ground state.