Origin of Ising magnetism in Ca 3 Co 2 O 6 unveiled by orbital imaging

The one-dimensional cobaltate Ca$${}_{3}$$Co$${}_{2}$$O$${}_{6}$$ is an intriguing material having an unconventional magnetic structure, displaying quantum tunneling phenomena in its magnetization. Using a newly developed experimental method, $$s$$-core-level non-resonant inelastic x-ray scattering ($$s$$-NIXS), we were able to image the atomic Co $$3d$$ orbital that is responsible for the Ising magnetism in this system. We can directly observe that corrections to the commonly accepted ideal prismatic trigonal crystal field scheme occur in Ca$${}_{3}$$Co$${}_{2}$$O$${}_{6}$$, and it is the complex $${d}_{2}$$ orbital occupied by the sixth electron at the high-spin Co$${}_{\,\text{trig}\,}^{3+}$$ ($${d}^{6}$$) sites that generates the Ising-like behavior. The ability to directly relate the orbital occupation with the local crystal structure is essential to model the magnetic properties of this system. Ca$${}_{3}$$Co$${}_{2}$$O$${}_{6}$$ has an unconventional magnetic structure displaying quantum tunnelling phenomena in its magnetization. Here, the authors use s-core-level non-resonant inelastic X-ray scattering to image the atomic Co 3d orbital that is responsible for the Ising magnetism in this system.