Finally, we note that spin-orbit coupling modulates the magnetic moment at low temperatures. To probe this possibility, we performed zero-field splitting (ZFS) calculations including spin-orbit interactions using both multi-reference (for local ZFS) and coupled-perturbed DFT methods, which are presented in Section S3 (and Table ) of the SI. Our results suggest that the effects of zero-field splitting may become increasingly important at low-temperature regions, especially for T < 50 K. Therefore, the χT at lower temperatures 25K < T < 90K (just before the S=0 starts becoming the ground state) will be affected due to the g and D parameters and hence can deviate significantly from the perfect S =1 magnetic moment.