Dresden 2014 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 20: Correlated Electrons: Spin Systems and Itinerant Magnets - Frustrated Magnets II

TT 20.10: Vortrag

Montag, 31. März 2014, 17:30–17:45, HSZ 304

Hour-glass magnetic spectrum in a stripeless insulating transition metal oxide — •Jan Yvo Drees¹, Daniel Lamago², Andrea Piovano³, and Alexander C. Komarek¹ — ¹Max-Planck-Institute for Chemical Physics of Solids, Physics of Correlated Matter, Nöthnitzer Street 40, D-01187 Dresden, Germany — ²Laboratoire Léon Brillouin, CEA/CNRS, F-91191 Gif-sur Yvette, France — ³Institut Laue-Langevin (ILL), 6 Rue Jules Horowitz, F-38043 Grenoble, France

An hour-glass-shaped magnetic excitation spectrum appears to be a universal characteristic of the high-temperature superconducting cuprates. Fluctuating charge stripes or alternative band structure approaches are able to explain the origin of these spectra. Recently, an hour-glass spectrum has been observed in an insulating cobaltate, thus favouring the charge stripe scenario. Here we show that neither charge stripes nor band structure effects are responsible for the hour-glass dispersion in a cobaltate within the checkerboard charge-ordered regime of La_2−xSr_xCoO₄. The search for charge stripe ordering reflections yields no evidence for charge stripes in La_1.6Sr9.4CoO₄, which is supported by our phonon studies. With the observation of an hour-glass-shaped excitation spectrum in this stripeless insulating cobaltate, we provide experimental evidence that the hour-glass spectrum is neither necessarily connected to charge stripes nor to band structure effects, but instead, probably intimately coupled to frustration and arising chiral or non-collinear magnetic correlations.