MAGNETIC AND TRANSPORT-PROPERTIES OF MAGNETITE IN THE VICINITY OF THE VERWEY TRANSITION

Systematic investigations concerning the variation of the Verwey phase transition in magnetite Fe3(1-δ)O4 on the metal-to-oxygen ratio by electrical resistivity, Seebeck coefficient, and magnetization measurements are reported, together with electrical properties of Fe3-xZnxO4 zinc ferrites. In conformity with earlier heat capacity measurements it has been documented that the transition temperature is significantly reduced with increasing δ. In the range 0 < δ < δc = 0.0039 the transition is of first order, whereas for δc < δ ≤ 0.012 it is of second (or higher) order. The electrical properties and Verwey transition of Fe3-xZnxO4 and Fe3(1-δ)O4 were found to match very well with the compositional correspondence x ⇔ 3δ. Implications of the above findings are discussed. © 1990.