Determination of the g-factors measured by EPR based on theoretical crystal field and superposition model analyses for lanthanide-based magnetically concentrated crystals – case study: double tungstates and molybdates

ABSTRACT

The methods developed for theoretical determination of g-factors measured by electron paramagnetic resonance (EPR) for single transition ions are extended to lanthanide-based magnetically concentrated crystals. The crystal field (CF) and superposition model (SPM) analyses are employed for optoelectronic materials: double tungstates and molybdates. Using the crystallographic data for Nd³⁺ ions in RbNd(WO₄)₂ and Yb³⁺ ions in KYb(MoO₄)₂ as input for SPM modelling, the CF parameters (CFPs) are predicted for the respective ions. The matrix for g tensor is calculated by the complete diagonalisation method. By matching three principal g values (g_xx, g_yy, g_zz) to those measured by EPR, three adjustable SPM intrinsic parameters:, and are obtained. The reliability of the related CFPs is verified by comparative analysis of available data. The results demonstrate that the methods suitable for single lanthanide ions in crystal can be successfully applied to magnetically concentrated systems. The predicted g tensor anisotropy enables consideration of EPR linewidths arising from dipolar broadening in ALn(MO₄)₂ (A = alkali ions, Ln = lanthanide ions, M = W or Mo) systems based on the moment method, which requires accurate g-factors. The model parameters determined here may be utilised for SPM/CFP calculations for Nd³⁺ and Yb³⁺ ions in single-molecule magnets and single-ion magnets.

KEYWORDS:

• EPR
• dipolar broadening
• magnetically concentrated crystals
• superposition model
• lanthanide-based tungstates and molybdates

Acknowledgements

One of us (Hong-Gang Liu) is also grateful to Prof. Yau Yuen Yeung of The Education University of Hong Kong for providing us with the “f-Spectra” computer package. The authors are grateful to Mrs H. Dopierała for technical help with references.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant numbers 11404229, 51574054]; Polish National Science Center [grant number UMO-2016/21/B/ST4/02064].