Spin-polarized interface states at the Pd(111)/Fe(110), Pd(111)/Co(0001), and Pt(111)/Co(0001) interfaces

Abstract

The spin-resolved electronic structure of epitaxial Pd overlayers on Fe(110) and on Co(0001) and of Pt overlayers on Co(0001) has been investigated by means of spin-resolved as well as spin-integrated, angle-resolved photoemission spectroscopy. Valence-band energy-distribution curves (EDC’s) for thin overlayer films show at the Γ¯ point of the surface Brillouin zone overlayer-induced peaks at -1.5 eV binding energy for Pd/Fe, -1.3 eV for Pd/Co, and -1.2 eV for Pt/Co. These states saturate in intensity for overlayer thicknesses between 1 and 1.5 atomic layers (AL) and do not disperse with ${}_{\mathrm{\perp }}{}^{}{}_{}{}^{}$, the component of the photoelectron wave vector normal to the film surface. This behavior indicates interface state character for these states, which have mainly Pd 4d or Pt 5d character. The spin-resolved EDC’s of these interface states reveal spin components with a peak separation of about 200±50 meV, whereby the minority-spin peak is more tightly bound than the majority-spin peak in all cases. For overlayer thicknesses of about 2–3 AL the development of a second interface state near -0.6 eV binding energy with no measurable peak separation of its spin components has been observed in all systems. Above about 5 AL thickness bulk Pd(111) and Pt(111) states are found for which no spin polarization is evident.