Spin-Exchange Processes in Inelastic Electron Scattering from Metals

Spin-flip electronic transitions have been recently observed in ferromagnetic metals by electron energy loss spectroscopy (EELS) with spin analysis. The strong energy dependence of the exchange excitation process involved allows the identification of these transitions also by ordinary EELS by taking the ratio of spectra obtained with low energy and high energy primary electrons. In rare-earth metals dipole-forbidden transitions between f levels with and without spin-flip are observed as the strongest features in the EELS spectra at low primary electron energies. In iron the spin-flip transitions (Stoner excitations) give mrise to an additional contribution at about 2 eV in the EELS spectra at low primary energies. The energy of the Stoner excitation is found to be constant up to the Curie temperature.