XMCD studies on honeycomb lattice antimonate Na3Co2SbO6 single crystals

The materials containing 4d^5 and 5d^5 transition metal ions with large spin-orbit coupling (SOC) are considered as candidate materials displaying J_eff = 1/2 magnetism and Kitaev quantum spin liquid ground state. Recently, it has been theoretically predicted that the Kitaev model can also be realized in 3d materials with Co2+ d^7 electronic configuration. Even though the SOC is smaller in 3d ions, J_eff =1/2 pseudospin magnetism can be expected. We would like to perform XAS and XMCD measurements at the Co L2,3 edges of Na3Co2SbO6 single crystals with honeycomb lattice structure to investigate whether this material hosts J_eff =1/2 ground state. From the experimental determination of the branching ratio from the XAS spectra, which is proportional to the spin orbit coupling, and by determining the ratio of the orbital to spin moment <Lz/2Sz> from the XMCD sum rule, we will obtain a direct information about the ground state of this material.