Quantifying uncertainties in crystal electric field Hamiltonian fits to neutron data

TL;DR

This paper investigates the uncertainties in fitting crystal electric field Hamiltonians to neutron scattering data, revealing significant parameter uncertainties even with good fits, especially in Yb$^{3+}$ compounds, highlighting the need for additional constraints.

Contribution

It systematically quantifies uncertainties in CEF parameter fitting to neutron data using specific material structures, emphasizing the importance of constraints for reliable results.

Findings

Uncertainty in CEF parameters can be large despite good fit quality.

Yb$^{3+}$ compounds exhibit particularly large $g$-tensor uncertainties.

Additional constraints are necessary for meaningful fits in certain cases.

Abstract

We systematically examine uncertainties from fitting rare earth single-ion crystal electric field (CEF) Hamiltonians to inelastic neutron scattering data. Using pyrochlore and delafossite structures as test cases, we find that uncertainty in CEF parameters can be large despite visually excellent fits. These results show Yb$^{3+}$ compounds have particularly large $g$-tensor uncertainty because of the few available peaks. In such cases, additional constraints are necessary for meaningful fits.