Comparative Raman scattering study of crystal field excitations in Co-based quantum magnets

Co-based materials have recently been explored because of their potential to realize complex bond-dependent anisotropic magnetism. Prominent examples include Na2Co2TeO6, BaCo2(AsO4)2, Na2BaCo(PO4)2, and CoX2 (X=Cl,Br,I). In order to provide insight into the magnetic interactions in these compounds, we make a comparative analysis of their local crystal electric field excitations spectra via Raman scattering measurements. Combining these measurements with theoretical analysis confirms the validity of jeff=1/2 single-ion ground states for all compounds, and provides accurate experimental estimates of the local crystal distortions, which play a prominent role in the magnetic couplings between spin-orbital coupled Co moments.