The Magnetic Structure of Fe₂As

Abstract

The magnetic structure of Fe 2 As has been determined by neutron diffraction. The compound Fe 2 As is antiferromagnetic with the Néel point at about 80°C. Its magnetic structure is different from Mn 2 As. The coupling between layers of iron atoms Fe(II) located at (0, 1/2, z ) and (1/2, 0, \bar z ) is antiparallel, but the coupling between a layer of iron atoms Fe(I) located at (0, 0, 0), (1/2, 1/2, 0) and adjacent Fe(II) layers is parallel. The magnetic unit cell has the c -axis twice as large as that of the chemical unit cell. The magnetic moments are 1.28 and 2.05 Bohr magnetons for Fe(I) and Fe(II) atoms. respectively. The moments lie perpendicular to the c -axis.