Interpretation of the optical absorption spectrum and of the paramagnetic susceptibility of neodymium A-type sesquioxide

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Abstract
A‐Nd2O3 is a layer structure built on the (NdO)n+n cation. Data for the 4.2 K optical spectrum and the strongly anisotropic parallel and perpendicular paramagnetic susceptibilities between 4 and 1000 K measured on single crystals, are reproduced using a Hamiltonian, that involves 12 free atom parameters (three Racah’s parameters, the spin–orbit coupling constant, Trees’ parameters α and β, and Judd’s six Tk operators) and six C3v crystal field parameters. The Hamiltonian operates on the 364 kets in 4f3, that is including J mixing. 88 Stark levels (from 0 to 34 000 cm−1) were fitted to a mean square deviation of 17 cm−1. The crystal field parameters (Wybourne’s formalism) are B20=−836 cm−1, B40=634 cm−1, B43=−1606 cm−1, B60=752 cm−1, B63=237 cm−1, B66=672 cm−1. The spectrum is strongly displaced to the red with respect to Nd3+ in LaCl3 and this is due to a lowering of Slater’s integrals F2 and F4 by 2% to 3%. The F6 integral is unchanged. The spin–orbit coupling constant is also lowered by 2%. The interaction parameters are slightly affected.