Magnetic Structure of Fe2As

Abstract

Magnetic structure of single crystal of Fe2As, which corresponds to C38 type of crystal structure, the same as that of Mn2Sb, has been determined by neutron diffraction method. The crystal is antiferromagnetic with the Néel temperature of approximately 50°C. A series of (00l)-type reflections at room temperature reveals magnetic superstructure reflections at (001/2), (003/2), (005/2), and (007/2). These reflections disappear when the temperature of the specimen is elevated to 50°C, whereas the main reflections do not show any changes within the experimental error. One of the remarkable features of the relative intensities of the superstructure reflections is that the (003/2) reflection is considerably weak relative to (005/2). From these results it can be concluded that this crystal has such an antiferromagnetic arrangement that FeII, FeI, and FeII atoms, each on three successive layers parallel to the (001) plane, form a group in which the magnetic moments are parallel to one another, and these moments are antiparallel to those of the neighboring groups. The [001] spacing of the magnetic unit cell is two times as large as that of the chemical unit cell.