Optical Investigations of YbCrO₃. I. Optical Absorption Spectra of Yb³⁺ Ion

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The optical transition ²F_7⁄2→²F_5⁄2 of Yb³⁺ in the antiferromagnet YbCrO₃ has been studied. The exchange splittings for the ground and excited Kramers doublets were observed in the antiferromagnetic state. From the analysis of the splitting of the ground Kramers doublet as a function of applied magnetic field, it is concluded that main Cr–Yb magnetic interactions are the Dzyaloshinsky-Moriya antisymmetric and the anisotropic-symmetric exchange interactions, which cause the splittings of the Kramers doublets in the absence of the external magnetic field. Besides single-ion excitations, a cooperative transition corresponding to the simultaneous excitation of the ²F_7⁄2→²F_5⁄2 transition on a Yb³⁺ ion and a spin flip of the ground doublet on its neighbouring Yb³⁺ ion was observed.