Experimental existence and nature of the predicted low-lying crystal-field doublet

Establish whether DyOCl possesses the low-lying excited Kramers doublet near 0.73 meV predicted by constrained point-charge crystal-field models, and determine whether the failure to observe its neutron transition reflects an unconstrained crystal-field level scheme or interaction-induced renormalization.

Background

The crystal-field model for DyOCl reproduces the observed excitations near 24 and 29 meV and predicts a second Kramers doublet approximately 0.73 meV above the ground-state doublet. Dedicated HYSPEC and DCS measurements, however, do not resolve a reproducible magnetic excitation in the predicted 0.3–0.8 meV range.

The absence of the predicted transition leaves the low-energy crystal-field scheme experimentally unsettled. The authors identify two possibilities: the high-energy powder spectrum may not uniquely constrain the low-energy levels, or interactions omitted from the single-ion model may substantially renormalize them.