Graphene grown on Co(0001) films and islands: Electronic structure and its precise magnetization dependence

We achieve epitaxial growth of graphene on the ferromagnetic substrate Co(0001) by chemical vapor deposition using propylene. Structural and electronic properties are revealed by means of low-energy electron diffraction, scanning tunneling microscopy, and spin-and angle-resolved photoelectron spectroscopy. The results are compared to those of graphene/Ni(111) for which a magnetization-dependent Rashba effect has recently been reported. Bulklike Co(0001) films on W(110) can be separated into islands by heating, and subsequently they can be covered by graphene. Such system is used to present unambiguous proof that in graphene/Co(0001) there is no Rashba effect and no intrinsic dependence of the band dispersion on the magnetization occurs. The high spin polarization of secondary electrons reported for graphene/Ni(111) is confirmed for graphene/Co(0001) with higher values (similar to 25%) due to the larger magnetic moment of Co.