Difference in spin state and covalence between La1-xSrxCoO3 and La2-xSrxLi0.5Co0.5O4

Hu, Z and Grazioli, C and Knupfer, M and Golden, MS and Fink, J and Mahadevan, Priya and Kumar, Ashwani and Ray, Sugata and Sarma, DD and Warda, SA and Reinen, D and Kawasaki, S and Takano, M and Schussler-Langeheine, C and Mazumdar, C and Kaindl, G (2002) Difference in spin state and covalence between La1-xSrxCoO3 and La2-xSrxLi0.5Co0.5O4. In: Journal of Alloys and Compounds, 343 (1-2). pp. 5-13.

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Abstract

We present a comparative study of the spin states and electronic properties of La1-xSrxCoO3 and La2-xSrxLi0.5Co0.5O4 using X-ray absorption near-edge structure spectroscopy at both the O-K and Co-L-2.3 thresholds. In the La2-xSrxLi0.5Co0.5O4 system the CoO6 octahedra are isolated, the holes induced by Sr doping are trapped in the isolated Co(IV)O-6 octahedra, and a low-spin state is found for the Co ions, which does not change upon Sr doping. In the La1-xSrxCoO3 system, the interconnected CoO6 octahedra, with a 180degrees Co-O-Co bond angle, give rise to a transition from low-spin to intermediate-spin state with a ferromagnetic alignment of the Co spins. The double-exchange, ferromagnetic coupling between Co ions mediated by the 180degrees bond angle is responsible for suppressing the low spin-state. We find that the branching ratio of spectral intensities at the L-2 and L-3 thresholds in the Co-L-2.3 X-ray absorption spectra is sensitive to the spin state of the Co ions allowing its direct spectroscopic determination. (C) 2002 Published by Elsevier Science B.V.

Item Type:	Journal Article
Publication:	Journal of Alloys and Compounds
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Keywords:	Rare earth compounds;Transition metal compounds;X-ray spectroscopy;Magnetic properties;Electronic properties
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	21 Jul 2011 07:16
Last Modified:	21 Jul 2011 07:16
URI:	http://eprints.iisc.ac.in/id/eprint/39143

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