Coexistence of distinct Ce 4f-electron states at inequivalent crystallographic sites: CePtGe2 case

In CePtGe ₂, which has two crystallographically inequivalent Ce sites, the coexistence of a localized magnetic 4f-electron state at one Ce site and an itinerant heavy-electron state at the second one has been suggested. We prepared a series of pseudoternary (Ce _xY _{1− x})PtGe ₂ compounds and investigated them by X-ray diffraction, magnetization, and specific heat measurements. The structure analysis revealed that the Y ions selectively occupy the Ce sites at the 4h position, which is more suited for smaller Ce ions with the itinerant heavy-electron state. The Néel temperature, low-temperature saturation magnetization, and magnetic entropy change weakly in the interval 1.0 ≥ x ≥ 0.5 while the linear specific-heat coefficient decreases rapidly with decreasing x. Further substitution of Y for Ce leads to a rapid decrease of the Néel temperature, low-temperature saturation magnetization, a remaining low linear specific-heat coefficient, and finally vanishing antiferromagnetism. These results corroborate the scenario of the coexistence of the magnetic Ce ions with localized 4f electrons responsible for the ordered magnetic state hosted by the 4i site, whereas the Ce ions at the 4h site are characterized by itinerant heavy 4f electrons.