X-Ray Diffraction Study on CoO

Low temperature x-ray diffraction experiment were performed to investigate the crystal symmetry of antiferromagnetic CoO and its domain structure. A new rhombohedral deformation was found in addition to the well known tetragonal deformation. The experimental result is consistent with the magnetic structure found by Roth, and can be interpreted by Kanamori's theory. Two types of magnetic domains were found to exist in CoO, as are expected from the magnetic structure and the related lattice deformations.