Properties of Cobaltous Oxide: Effects of Gas Absorption and External Magnetic Fields

Abstract

We have extended our earlier studies of cobaltous oxide, form II, investigating the oxidation properties in greater detail and examining the effects of large external applied magnetic fields. We find that CoO(II) strongly picks up oxygen at room temperature, with excess oxygen exceeding 60% after long exposures. By contrast, ${\mathrm{N}}_2$, Ar, and Ne are only slightly adsorbed by this material. The effect of applying a 47.5-kG magnetic field is to selectively broaden the hyperfine pattern. We discuss these results in relation to recent proposed models on the structure of cobaltous oxide. We conclude that none of the simpler models suggested for this material is completely satisfactory in explaining all of the data. The data appear to require a high porosity as well as a significant concentration of point defects, and suggest a spongelike structure possibly resulting from sintered microcrystals. The way in which CoO(II) selectively absorbs oxygen may make it a useful material in applications requiring a room-temperature oxygen getter.