Donut-shaped orbitals and Ising magnetism in Ca3Co2O6

Donut-shaped orbitals and Ising magnetism in Ca₃Co₂O₆. The research teams of Hao Tjeng from the MPI-CPfS, Andrea Severing from the University of Cologne, Antoine Maignan from CRISMAT Laboratory Caen, and Maurits Haverkort from the University of Heidelberg have succeeded in determining the electronic orbital that is responsible for the Ising magnetism in Ca₃Co₂O₆. A direct image of the donut-shaped orbital has been made using the new Max Planck end-station at German Electron Synchrotron DESY in Hamburg. Ca₃Co₂O₆ is a very peculiar material. It shows stair-step jumps in the magnetization at regular intervals with an increasing applied field strength, which is indicative of the presence of quantum tunneling phenomena. Numerous theoretical and experimental studies have been carried out to explain the properties of Ca₃Co₂O₆ and its close derivatives. These intriguing properties have their origin in the unusual arrangement of the atoms in this material type: one-dimensional chains are formed along the c'axis with alternating CoO₆ octahedra and trigonal prisms, and in the ab-plane, the chains form a triangular-type lattice.