Verwey transition
An electron-ordering transition occurring in a mixed-valent system that results in an ordering of formal valence states in the low-temperature phase. Example: The prototype system, first identified by Verwey, is the ferrospinel magnetite, Fe3+[Fe3+Fe2+]O4 in which an ordering of Fe3+ and Fe2+ ions within octahedral sites is thought to occur below T v ≈ 120 K.
PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 593 (