  The one-dimensional cobaltate Ca3Co2O6 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 show that we can directly observe that it is the complex d2 orbital
occupied by the sixth electron at the high-spin Co-trig{3+} (d6) sites that
generates this behavior. This is extremely rare in the research field of
transition metal compounds, and is only made possible by the delicately
balanced prismatic trigonal coordination. The ability to directly relate the
orbital occupation with the local crystal structure is essential to model the
magnetic properties of this system.
