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MA: Fachverband Magnetismus

MA 55: Poster II

MA 55.46: Poster

Freitag, 4. April 2014, 10:30–13:30, P2

Dispersive Magnon Excitations in Ca₃Co₂O₆ — •Pavlo Y. Portnichenko², Anil Jain¹, Hoyoung Jang¹, Alexandr Ivanov³, Bernhard Keimer¹, and Dmytro S. Inosov² — ¹Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, 70569 Stuttgart, Germany. — ²Institut für Festkörperphysik, TU Dresden, Zellescher Weg 16, D-01069 Dresden, Germany. — ³Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex, France.

The geometrically frustrated trigonal cobaltate Ca₃Co₂O₆ is considered to be a model system for a one-dimensional Ising-like antiferromagnet. Its crystal structure represents a hexagonal arrangement of one-dimensional chains, which consist of alternating nonmagnetic CoO₆ octahedra and CoO₆ trigonal prisms with a large magnetic moment.

Using inelastic neutron scattering, we have observed a quasi-one-dimensional dispersive magnetic excitation in the frustrated triangular-lattice spin-2 chain oxide Ca₃Co₂O₆. At the lowest temperature (T= 1.5 K), this magnon is characterized by a large zone-center spin gap of ∼ 27 meV, which we attribute to the large single-ion anisotropy, and disperses along the chain direction with a bandwidth of ∼ 3.5 meV. In the directions orthogonal to the chains, no measurable dispersion was found. With increasing temperature, the magnon dispersion shifts towards lower energies, yet persists up to at least 150 K, indicating that the ferromagnetic intrachain correlations survive up to six times higher temperatures than the long-range interchain antiferromagnetic order.