Structural and magnetic characterization of the lithiated iron oxide LixFe3O4

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Abstract
The Rietveld profile-analysis method is used to investigate the x-ray diffraction pattern of lithiated Fe3O4. It is shown that, after exposure to air, pure magnetite coexists with a lithium-inserted LixFe3O4 phase. The Mössbauer spectra at 300 and 4.2 K have been used to estimate the lithium content of the sample, the pure magnetite concentration, and the iron distribution over the available 16c and 16d sites of the spinel structure. Magnetization measurements from 4.2 to 120 K with an external magnetic field up to 150 kOe have been used to obtain the saturation magnetic moment, the magnetic anisotropy constants, and the susceptibility. It is concluded that a noncollinear spin structure should be present in Li0.5Fe3O4. These results indicate that there is no room-temperature extrusion of iron even for x→2.0, but that on exposure to air LixFe3O4 samples with x>0.5 are oxidized at room temperature by delithiation.