The effect of doping on global lattice properties of magnetite Fe3−xMexO4 (Me=Zn, Ti and Al)

X-ray powder diffraction was measured in Fe3−xMexO4 (Me=Zn, Ti, Al; x<0.065), in T range 70–300 K to see the effect of different doping on global lattice properties. The experimental results have shown that some lattice properties (e.g., the cell volume) are dopand specific. This can be attributed to the difference in preferential sites occupation by dopants. As confirmed by EXAFS, Zn enters tetrahedral, while Ti octahedral lattice sites, differently affecting crucial octahedral iron positions in the spinel lattice. However, despite this fact, it was found that T dependence of both monoclinic angle and lattice parameters is universal for studied samples above and below the Verwey transition temperature TV. So, not the iron atoms in octahedral positions individually, but interactions between them are responsible for the Verwey transition character change with doping.

A low temperature magnetite cell volume vs. dopants content. Apparently, Zn, Ti and Al atoms have different effect on the global lattice properties at individual temperatures. However, the Verwey transition reacts to dopants in a similar manner, despite the different way the octahedral iron positions are affected.Figure optionsDownload as PowerPoint slideHighlights
► We measure powder diffraction and EXAFS on Fe3−xMexO4, Me=Zn, Ti, Al (x<0.065), in T range 70–300 K.
► XRD: atom-type independent changes of lattice parameters with T.
► EXAFS: Zn replaces Fe on tetrahedral positions, Ti on octahedral positions.
► Thus, some secondary interactions between ordering orbitals, not the primary one driving the Verwey transition, control the transition order.