Image states at ferromagnetic surfaces: Fe(110), (100), (111) and Co(0001)

Image states are observed on Fe(110), Fe(100), Fe(111), and Co(0001) with inverse photoemission. Their energies are 4.4, 3.7, 3.9, and 4.5 eV above the Fermi level, respectively. The magnetic splitting of these states is estimated using a phase-shift model, and values in the 0.03-eV range are obtained. The splitting is calculated to increase to more than 0.1 eV for image states close to the band edges of the supporting bulk band gap. Such a splitting would make it possible to create a spin-polarized, two-dimensional electron gas by selectively pumping the majority-spin image state with a laser.