Spin-correlation imaging of electrons in ferromagnets

The angular and energy dependencies of the exchange interaction between the electrons in an itinerant ferromagnetic surface can be mapped out by exciting two interacting spin-polarized electrons into the vacuum and resolving at the same time the energies and emission angles of the two electrons. From a tensorial symmetry analysis it is deduced that the recorded two-particle spectra carry detailed information on the spin-split electronic structure that can be extracted under favorable conditions. To substantiate these statements we present and analyze experimental results and numerical calculations for a ferromagnetic iron surface.