Positron Annihilation in Ferromagnetic Nickel

The angular correlation of annihilation radiation in ferromagnetic nickel single crystals has been measured by using standard parallel-slit system with a newly developed 90 Nb positron source. The crystals were oriented in the [100] and [110] directions. The observed angular distribution curves were anisotropic with appreciable structures. Interpretation of the angular distribution in terms of the shapes of the Fermi surfaces alone were not successful, indicating that consideration of the Bloch character of the electrons in 3d bands is important.