MAGNETISM OF SURFACES BY SPIN POLARIZED PHOTOEMISSION

Spin polarized photoemission is used as a method to study the magnetic peoperties of solid surfaces. Here we consider those systems where the spin polarization is believed to be conserved during the photoemission process. The surface sensitivity of the experiment will be therefore mainly determined by the relative magnitudes of the escape depth ℓ of the photoelectrons and of the magnetic coherence length ξ. We analyze both the temperature and magnetic-field dependence of the degree of spin polarization P of the electrons emitted from single crystals of magnetite, Fe3O4, and thin films (D=2-3000 Å) of Fe, Co and Ni. These data yield information on 1) the temperature dependence of the magnetization of the surface, 2) the relative sizes of ξ and ℓ, 3) changes of the magnetic moment of atoms in the surface layers, and 4) the surface magnetic anisotropy. We show that this technique emerges as a novel tool to study magnetic systems with free surfaces and to test the predictions of recent calculations of the magnetic properties of surfaces. Emphasis is given to the fact that only relative changes of P and not its absolute values are relevant for an analysis of the data. © 1979 Springer-Verlag.