Seebeck coefficient of magnetite: a reinterpretation invoking Jahn-Teller entropy

Abstract

The Seebeck coefficient of stoichiometric F_e3O₄ has been measured at high temperature in a controlled CO + CO₂ gas atmosphere. Assuming small polaron transport via octahedral sites, the cation distribution between the tetrahedral and octahedral sites of the spinel is obtained as a function of temperature from the Seebeck coefficient. The temperature dependence of cation distribution is explained by a new model in which the entropy arising from randomization of the Jahn-Teller distortion is incorporated. It is unnecessary to postulate that the enthalpy change for the cation interchange reaction is a linear function of the cation disorder parameter.