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Magnétisme de quelques composés bidimensionnels de la famille AMO2 (A=Li, Na: M=Ni, Fe, Co)

Abstract : We present a study of the magnetic properties of layered oxides that belong to the AMO2 family (A=Li, Na; M=Ni, Fe, Co). The compounds are very promising materials for battery applications. LiNiO2 is the subject of strong theoretical interest due to the possible coupling between spin and orbital degrees of freedom. Several works have been devoted to the magnetic properties of LiNiO2 but the results remain much debated. Since this is also crucial for battery capacity, solid state chemists have improved the synthesis and the characterisation of the samples these last years. It has been shown that both electrochemical and magnetic properties are very sensitive to the departure from the stoichiometry. The magnetic properties of the perfectly lamellar NaNiO2 system have been first studied by means of electron spin resonance, neutron diffraction, high field magnetization and low field susceptibility. NaNiO2 is an A-type antiferromagnetic insulator with a ferrodistorsive orbital ordering for T<210°C due to the cooperative Jahn-Teller effect of the Ni3+ ions in the low spin state S=1/2. A detailed study of the Li1-xNi1+xO2 solid solution is also provided, showing the fundamental role of extra Ni ions which induce magnetic clusters progressively formed and oriented with increasing x. Based on the determination of the magnetic interactions, we propose an original model of a cluster induced frustration which explains both the spin-glass like behaviour at low temperatures for the quasi-stoichiometric compound and the large spectrum of magnetic behaviours observed for Ni rich compounds. After a magnetic characterization of the lamellar LiFeO2, we finally consider the effect of cationic substitution of cobalt in LiFeO2 and iron in LiNiO2. We show that iron ions on the lithium site do not induce magnetic clusters. For all samples, the sign and the intensity of the magnetic interactions are given.
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https://tel.archives-ouvertes.fr/tel-00008226
Contributor : Eric Chappel <>
Submitted on : Friday, January 21, 2005 - 8:34:14 PM
Last modification on : Friday, November 6, 2020 - 3:46:24 AM
Long-term archiving on: : Friday, April 2, 2010 - 9:18:49 PM

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  • HAL Id : tel-00008226, version 1

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Eric Chappel. Magnétisme de quelques composés bidimensionnels de la famille AMO2 (A=Li, Na: M=Ni, Fe, Co). Matière Condensée [cond-mat]. Université Joseph-Fourier - Grenoble I, 2000. Français. ⟨tel-00008226⟩

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