ELECTRON MICROSCOPY OF ORTHORHOMBIC PHASE IN MAGNETITE

An electron microscopic observation on a synthetic single crystal of magnetite has been carried out at a temperature range between 77°K and room temperature. It was observed that the ordered phases below the low-temperature transition appear as finely divided stripes. The diffraction patterns in one of the stripes show the extra spots such as (00½), (100), (010), or (11½) in cubic indices. This indicates that the unit cell of the low-temperature phase should be twice as large as that proposed by Verwey. The ordering scheme proposed should be more complicated than the Verwey order.