Spin Motion of Electrons Upon Reflecting From Ferromagnetic Surfaces

When electrons are reflected from a ferromagnetic surface, their spin polarization vector is expected to move. This spin motion, comprising an azimuthal precession and a polar rotation about the magnetization direction of the ferromagnet, has been measured in a spin-polarized electron scattering experiment. Measurements on polycrystalline Fe, Co, and Ni films reveal a strong spin precession at low primary electron energies. This observation is explained by the existence of spin-dependent gaps in the electronic band structure of the ferromagnets. Because of total angular momentum conservation the electron-spin motion signals that a torque is exerted on the magnetization by the incident electrons