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Charge correlations in cobaltates La 2– x Sr x CoO 4
Author(s) -
Guo H.,
Schmidt W.,
Tjeng L. H.,
Komarek A. C.
Publication year - 2015
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.201510290
Subject(s) - ion , charge ordering , charge (physics) , doping , spins , blueshift , materials science , phase (matter) , analytical chemistry (journal) , condensed matter physics , physics , chemistry , optics , photoluminescence , quantum mechanics , chromatography
We report on an elastic neutron scattering study of the charge correlations in La 2– x Sr x CoO 4 with x = 1/3, 0.4 and 0.5. We found that the checkerboard charge ordering correlations present in the x = 0.5 sample persist in the x = 0.4 and 1/3 materials. These checkerboard charge ordering correlations are robust and explain the occurrence of nano‐phase separation in layered cobaltates for Sr‐concentrations away from half‐doping. The half‐integer reflections then arise from the nanometer‐sized hole‐rich regions (blue areas in title figure) instead of the undoped ones (red areas in title figure). The appearance of nano‐phase separation is an important ingredient for understanding the formation of hour‐glass shaped magnetic excitation spectra in La 2– x Sr x CoO 4 .Nano‐phase separation in La 2– x Sr x CoO 4 (schematically). Red areas: undoped La 2 CoO 4 islands, blue areas: checkerboard charge ordered regions; black, green and blue balls represent nonmagnetic Co 3+ ions, magnetic Co 2+ ions and oxygen ions, respectively; green arrows indicate Co 2+ spins [1, 2]. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)