Incommensurate spin correlations in highly oxidized cobaltates La2-xSrxCoO4.
We observe quasi-static incommensurate magnetic peaks in neutron scattering experiments on layered cobalt oxides La2-xSrxCoO4 with high Co oxidation states that have been reported to be paramagnetic. This enables us to measure the magnetic excitations in this highly hole-doped incommensurate regime and compare our results with those found in the low-doped incommensurate regime that exhibit hourglass magnetic spectra. The hourglass shape of magnetic excitations completely disappears given a high Sr doping. Moreover, broad low-energy excitations are found, which are not centered at the incommensurate magnetic peak positions but around the quarter-integer values that are typically exhibited by excitations in the checkerboard charge ordered phase. Our findings suggest that the strong inter-site exchange interactions in the undoped islands are critical for the emergence of hourglass spectra in the incommensurate magnetic phases of La2-xSrxCoO4.
Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany.
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Li
Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany.
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Drees
Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany.
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Kuo
Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany.
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Guo
Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22603 Hamburg, Germany.
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Ricci
Forschungszentrum Karlsruhe, Institut für Festkörperphysik, P.O.B. 3640, D-76021 Karlsruhe, Germany.|Laboratoire Léon Brillouin, CEA/CNRS, F-91191 Gif-sur Yvette Cedex, France.
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Lamago
Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM-II), TU München, Lichtenbergstr. 1, D-85747 Garching, Germany.|Georg-August-Universität Göttingen, Institut föur Physikalische Chemie, Tammannstrasse 6, D-37077 Göttingen, Germany.
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Sobolev
Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22603 Hamburg, Germany.
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Rütt
Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22603 Hamburg, Germany.
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Gutowski
National Synchrotron Radiation Research Center (NSRRC) 30077, Hsinchu, Taiwan.
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Institut Laue-Langewin (ILL), 71 avenue des Martyrs, F-38042 Grenoble Cedex 9, France.
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Piovano
Institut Laue-Langewin (ILL), 71 avenue des Martyrs, F-38042 Grenoble Cedex 9, France.|Jülich Centre for Neutron Science JCNS, Forschungszentrum Jülich GmbH, Outstation at ILL, 71 avenue des Martyrs, F-38042 Grenoble Cedex 9, France.
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Schmidt
Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany.
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Mogare
Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany.
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Hu
Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany.
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Tjeng
Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany.
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Komarek