Magnetic dichroism in valence-band photoemission from Co/Cu(001): Experiment and theory

Optical Generation of Hot Spin-Polarized Electrons from a Ferromagnetic Two-Dimensional Electron Gas

Linearly polarized light with an energy of 3.1 eV has been used to excite highly spin-polarized electrons in an ultrathin film of face-centered-tetragonal cobalt to majority-spin quantum well states (QWS) derived from an sp band at the border of the Brillouin zone. The spin-selective excitation process has been studied by spin- and momentum-resolved two-photon photoemission. Analyzing the photoemission patterns in two-dimensional momentum planes, we find that the optically driven transition from the valence band to the QWS acts almost exclusively on majority-spin electrons. The mechanism providing the high spin polarization is discussed by the help of a density-functional theory calculation. Additionally, a sizable effect of spin-orbit coupling for the QWS is evidenced.

Spin-orbit hybridization points in the face-centered-cubic cobalt band structure

Linear magnetic dichroism is observed in spin-, time-, and energy-resolved two-photon photoemission from valence bands of epitaxial fcc cobalt on Cu(001). With image-potential states as spectator states we identify initial bulk and surface states with minority spin character as the source for dichroic intensities and apparent dichroic lifetimes. Excellent agreement with ab initio fully relativistic calculations of the cobalt fcc band structure allows us to precisely determine spin-orbit hybridization points close to the Fermi level. These spin hot spots enhance spin-flip scattering by several orders of magnitude and are therefore assumed to be crucial in ultrafast demagnetization.

Optical magnetic circular dichroism in threshold photoemission from a magnetite thin film

Threshold photoemission excited by polarization-modulated ultraviolet femtosecond laser light is exploited for phase-sensitive detection of magnetic circular dichroism (MCD) for a magnetite thin film. Magnetite (Fe(3)O(4)) shows a magnetic circular dichroism of ∼(4.5 ± 0.3) × 10(-3) for perpendicularly incident circularly polarized light and a magnetization vector switched parallel and antiparallel to the helicity vector by an external magnetic field. The asymmetry in threshold photoemission is discussed in comparison to the magneto-optical Kerr effect. The optical MCD contrast in threshold photoemission will provide a basis for future laboratory photoemission studies on magnetic surfaces.