Investigation of the electronic structure of ferro- and paramagnetic nickel by positron annihilation

Positron angular correlation curves have been measured for nickel in the [100], [110], and [111] directions at room temperature, 330°C and 380°C. Mijnarend's approach is used for their interpretation. For ferromagnetic nickel th 6th zone Fermi Surface (FS) obtained in this way is similar to that obtained from other experimental measurements as well as from band structure calculations. At 380°C the regrouping of the 5th zone electrons at the Curie point is well visible, and information is obtained about the paramagnetic nickel FS in the 6th and 5th zones. Besides, at this temperature the FS in the 6th zone is larger and rounded off. This effect, still needing further experimental confirmation, is attributed to thermal vibrations of the lattice.