Abstract
Atomic level observations have been made for the commensurate phase P″of Fe0.902O and the incommensurate phase P′of Fe0.920O by means of the high resolution electron microscopy. The crystal structure of the P″phase is monoclinic and belongs to the space group P21/m. The vacancy cluster is made of two vacancy tetrahedra with a common edge and contains no iron atom at the tetrahedral sites. In the real crystal, however, several kinds of structural disorder are introduced. [Jap. J. Appl. Phys. 24, L723 (1985) ] . In the P′phase, the cluster arrangement is almost cubic. The P′is essentially incommensurate without any domain structure.
