Magnetite single crystals Fe3-xMxO4 doped with M = Ni, Co, Mg;; Al, Ga, and
Ti were grown and annealed under a controlled atmosphere to produce homoge
neous and oxygen stoichiometric samples. The cation vacancy concentration o
f the samples was proved to be lower than 10(-6) by means of magnetic disac
commodation spectroscopy; The Verwey temperature shift as function of the s
ubstituent concentration was determined from the temperature dependence of
the resistivity. The systematics of the transition temperature shift as fun
ction of the concentration and nature of the substituents is indicative tha
t the mechanism of the transition is related to the second-neighbor Coulomb
interaction of the cations on the octahedral sites. [S0163-1829(98)00846-7
].