Crystal and magnetic structure of the system Li0.5+0.5xFe2.5-1.5xTixO4 (x=0.16, 0.44, and 0.72)

The influence of thermal treatment on the structure of lithium titanium ferrite spinels of general formula Li(0.5+0.5x)Fe(2.5-1.5x)Ti(x)O4 (x=0.16, 0.44, and 0.72) has been studied by X-ray and neutron diffraction and analysed by the Rietveld method. The results allow us to conclude the presence of an ordered phase (space group P4(3)32) at room temperature for the sample with x=0.16; this phase does not appear for the remaining compositions. The magnetic properties evidence a ferrimagnetic ordering in the structures when a random cation distribution (space group Fd3 m) is obtained. An exhaustive study carried out by neutron diffraction measurements on these samples shows a different behaviour when the titanium content is increased, concluding that the lower substituted phase (x=0.16) exhibits a Neel's collinear ferrimagnetic structure, with the higher substituted structures being noncollinear (x=0.44 and 0.72).