The behavior in magnetic field of a paramagnetic center is characterized by its g tensor. An anisotropic form of the latter implies different kind of response along different crystallographic directions. Here we shed light on the anisotropy of the g tensor of Yb3+ 4f13 ions in NaYbS2 and NaYbO2, layered triangular-lattice materials suggested to host spin-liquid ground states. Using quantum chemical calculations we show that, even if the ligand-cage trigonal distortions are significant in these compounds, the crucial role in realizing strongly anisotropic, `noncubic' g factors is played by inter-layer cation charge imbalance effects. The latter refer to the asymmetry experienced by a given Yb center due to having higher ionic charges at adjacent metal sites within the magnetic ab layer, i.e., 3+ nearest neighbors within the ab plane versus 1+ species between the magnetic layers. According to our results, this should be a rather general feature of 4f13 layered compounds: less inter-layer positive charge is associated with stronger in-plane magnetic response.
@article{arxiv.1909.01224,
title = {Single-site magnetic anisotropy governed by inter-layer cation charge imbalance in triangular-lattice AYbX$_2$},
author = {Ziba Zangeneh and Stanislav Avdoshenko and Jeroen van den Brink and Liviu Hozoi},
journal= {arXiv preprint arXiv:1909.01224},
year = {2019}
}