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

The optical transition 2 F 7/2 → 2 F 5/2 of Yb 3+ in the antiferromagnet YbCrO 3 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 Dzyaloshirnsky-Moriya antisymetric and the anisotropic-symetric 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 2 F 7/2 → 2 F 5/2 transition on a Yb 3+ ion and a spin flip of the ground doublet on its neighbouring Yb 3+ ion was observed.