2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/99180We find using LSDA+U band structure calculations that the novel one-dimensional cobaltate Ca$_3$Co$_2$O$_6$ is not a ferromagnetic half-metal but a Mott insulator. Both the octahedral and the trigonal Co ions are formally trivalent, with the octahedral being in the low-spin and the trigonal in the high-spin state. The inclusion of the spin-orbit coupling leads to the occupation of the minority-spin $d_{2}$ orbital for the unusually coordinated trigonal Co, producing a giant orbital moment (1.57 $μ_{B}$). It also results in an anomalously large magnetocrystalline anisotropy (of order 70 meV), elucidating why the magnetism is highly Ising-like. The role of the oxygen holes, carrying an induced magnetic moment of 0.13 $μ_{B}$ per oxygen, for the exchange interactions is discussed.5 pages, 4 figures, and 1 tableStrongly Correlated ElectronsMaterials Sciencetext