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1998 (2)
1996 (1)
1Author    C. B. Azzoni, M. C. Mozzati, A. Paleari, V. Massarotti, D. Capsoni, M. BiniRequires cookie*
 Title    Magnetic Order in Li-Mn Spinels  
 Abstract    Magnetic measurements were carried out on different samples of Lithium-Manganese spinel LiMn 2 0 4 , great care having been taken to avoid the presence of spurious magnetic phases, such as Mn 3 0 4 . Sus-ceptibility data, showing deviations from paramagnetic behaviour at about 40 K, were analyzed in terms of local magnetic interactions, taking into account the structural and transport properties of these com-pounds. The magnetic response of pure and stoichiometric samples suggests that the onset of a long-range magnetic ordering is hindered by the topological frustration of the antiferromagnetic octahedral sublattice of the spinel. 
  Reference    Z. Naturforsch. 53a, 693—698 (1998); received April 25 1998 
  Published    1998 
  Keywords    Magnetic Susceptibility, Electron Paramagnetic Resonance, Lithium Manganese Oxides, Lithium Manganese Spinel 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0693.pdf 
 Identifier    ZNA-1998-53a-0693 
 Volume    53 
2Author    V. Massarotti, M. Bini, D. CapsoniRequires cookie*
 Title    Structural and Defect Study of LiMn 2 0 4 Formation  
 Abstract    The LiMn 2 0 4 formation from MnO and Li 2 C0 3 mixtures with lithium cationic fraction 0.31 < x < 0.40 was studied by structural profile refinement from X-ray data, thermal (TGA and DSC) measurements and scanning electron microscopy (SEM) observations. Quantitative phase analysis, structural and microstructural parameters and composition of the coexisting phases were obtained. Different behaviours were observed in the composition ranges 0.33 < x < 0.35 and x > 0.37. In the former range only the stoichiometric spinel phase was obtained, in the latter, in addition to the Li 2 Mn0 3 compound, two spinel phases could be considered: I) LiMn 2 0 4 stoichiometric spinel; II) Li i +> Mn2-> .04 (0.11 < y < 0.23), a non-stoichiometric phase whose small particle size resulted practically independent of the initial composition and annealing temperature. Such a conclusion was supported also by SEM observations. The relative abundance of phase II increased with increasing lithium content and with decreasing temperature. 
  Reference    Z. Naturforsch. 51a, 267—276 (1996); received March 3 1996 
  Published    1996 
  Keywords    Solid state reaction, Lithium Manganese Spinel, Structural and microstructural parameters, Non-stoichiometry, Substitutional defects 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0267.pdf 
 Identifier    ZNA-1996-51a-0267 
 Volume    51 
3Author    V. Massarotti, D. Capsoni, M. Bini, C. B. Azzoni, M. C. Mozzati, A. PaleariRequires cookie*
 Title    Structural and Magnetic Characterization of Mixed Oxides: A Study of Li-Ni-O and Li-Mn-O Systems  
 Abstract    The present paper details the way to determine the cation distribution in mixed oxides with transition ions from the diffraction and magnetic susceptibility data. This approach allows one to determine phase abundances and phase compositions by two combined procedures. By X-ray diffraction Rietveld pro-file refinement and magnetic susceptibility data analysis it is possible to estimate the ratio and the oc-cupancy factor of paramagnetic ions in different oxidation states. A brief discussion of practical cases is reported. In the Li-Ni-0 system the lithium cationic fraction of the ordered phase Li 2r Ni2_2 X 0 2 in-creases monotonically with the total lithium fraction x, for 0.31 < x, < 0.46. In the Li-Mn-0 system for 0.36 < JC, < 0.53 the Li 2 Mn0 3 fraction has been determined, and for the coexistent Li [Li-y Mn 2 _ > ,] 0 4 spi-nel phase the dependence of y on x t has been evaluated. 
  Reference    Z. Naturforsch. 53a, 150—156 (1998); received January 30 1998 
  Published    1998 
  Keywords    X-ray Powder Diffraction, Magnetic Susceptibility, Lithium Nickel Oxides, Lithium Man-ganese Oxides, Lithium Manganese Spinel 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0150.pdf 
 Identifier    ZNA-1998-53a-0150 
 Volume    53