X-ray studies of Fe3−xMexO4, Me=Zn, Ti and Al; the impact of doping on the Verwey transition

We have performed structural X-ray studies of Fe3-xMexO4, where Me=Zn, Ti and Al in temperature range 70-300K. Very small doping by Zn, Ti or Al, studied here, greatly disturbs this strongly correlated electron-phonon system changing the Verwey transition temperature as well as transition character from discontinuous to continuous one. We discuss temperature dependence of lattice parameters determined by the Rietveld analysis for specimens showing different types of transition to find out whether the transition is already prearranged at high temperatures e.g. suggested by our elastic constant data. We also compare the change of the structure at the Verwey transition for these two classes of materials.