Properties of Single-Crystal CoO Films on MgO

Publisher Website
Google Scholar
Abstract
Single‐crystal CoO films, 3 to 30 μ thick, were grown epitaxially on MgO by halide decomposition. Optical, x‐ray, and magnetic torque measurements were made on the as‐grown samples, i.e., with the CoO attached to the MgO. Films with (001) and (111) orientations had a spiral growth structure. Twinning in the CoO films below the Néel temperature was investigated by optical and x‐ray techniques. Antiferromagnetic twin domains were observed in (001) CoO films at 77°K by transmitted polarized light. The tetragonal distortion in CoO was measured down to 83°K and had bulk values with a c/a ratio of 0.9880 at 83°K. Magnetic torque measurements were made from 77° to 296°K in fields up to 22 kOe. The symmetry and amplitude of the torque varied when the sample was cooled from room temperature in a field. Cooling in a field altered the spin axes distribution to favor those spin axes most perpendicular to the cooling field direction. The torque data for the (111) orientation were consistent with a single‐ and a multi‐spin‐axis model. However, the torque data for the (001) orientation were consistent only with a single‐spin‐axis model.