δ-Dependence of Magnetism in the C15 Laves Phase System HfCo2+δ

Investigations of the magnetic properties of non-stoichiometric HfCo₂+δ led to the discovery of ferromagnetism for δ ≫ 0.8. Homogeneous samples formed by plasma jet-melting in argon were annealed to obtain single phase crystals, and then quenched. X-ray diffraction confirmed the existence of a single-phase with C15 type structure for -0.2 ≪ δ ≪ 1.2, but a single phase could not be obtained at other compositions. The range of ferromagnetic behavior, susceptibility, and other magnetic properties are described.