Superparamagnetism and metal-site ordering in quaternary nitrides with the η-carbide structure

The synthesis and characterisation of Ni2GaMo3N and the family of compounds Fe3−xCoxMo3N, which crystallise with the η-carbide structure, are reported. A combination of magnetometry and diffraction experiments shows that they display Ni/Ga or Fe/Co metal-site ordering and, in the latter case, complex paramagnetism which does not vary in a uniform way with composition. All the compositions described here display metallic conductivity.