On Nickel Oxides of High Oxygen Content

Nickel oxides of high oxygen content formed by incomplete dissociation of nickel nitrate were investigated crystallographically and magnetically. The oxygen excess of these oxides ranges from zero to 0.2 gr. atom/mol., and their crystal structures are not essentially different from that of the ordinary nickel oxide. As they are not in a stable state, they have some curious but important behaviors. That is, with the degree of excess, they become to have a cubic structure the parameter of which is larger than that ( a ) of a rhombohedrally deformed one, and at sufficiently high oxygen contents they behave as something like a ferromagnetics. Such rather extraordinary phenomena may be considered to be originated from the fact that the oxygen excess in the specimens owes not only nickel vacancies but also the absolute excess of anions. In the measurements of susceptibility, the coincidency between the heating and cooling curves is very good for ferromagnetics-like oxides, while it is not for antiferromagnetic ones. There is also an evidence for the existence of antiferromagnetic cubic oxide at a temperature fairly lower than its Néel point.