Positron-annihilation study of the half-metallic ferromagnet NiMnSb: Theory.

Abstract

Calculations of the electronic structure, the Fermi surface, and the momentum density of annihilation photon pairs are presented in preparation for an experimental study of the half-metallic ferromagnet NiMnSb with the aid of the two-dimensional angular correlation of annihilation radiation technique. The band structure obtained is in good agreement with former calculations and consists of a metallic majority-spin and a semiconducting minority-spin band. The majority-spin Fermi surface consists of three \ensuremath{\Gamma}-centered hole sheets, two of which have necks at L. The different nature of the bands is clearly reflected in the spin-dependent momentum densities. From these densities a magnetic difference effect in the angular correlation can be derived which should be clearly observable with polarized positrons.