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.

• Received 8 May 1984

DOI:https://doi.org/10.1103/PhysRevB.31.430