Influence of nonstoichiometry on the Verwey transition

The dependence of the Verwey transition temperature on the nonstoichiometry of ${\mathrm{Fe}}_{3\left(1\mathrm{-}\mathrm{\delta }\right)}$ ${\mathrm{O}}_4$ has been characterized by thermomagnetic analysis of the initial permeability in magnetite single crystals subjected to subsolidus controlled oxygen fugacity annealing. Nonstoichiometry depresses the transition temperature, which is a maximum for δ=0. For extreme levels of cation deficiency, a second-order transition occurs at 120 K. An anomaly is reported at 250 K.