Magnetic circular dichroism in 4fphotoemission from terbium

Strong magnetic circular dichroism (MCD) in 4f photoemission from remanently magnetized films of Tb(0001) and ${\mathrm{TbFe}}_{\mathit{x}}$ grown on W(110) is reported. Asymmetries of up to 62% have been observed for the 4${\mathit{f}}^8$ ${\mathrm{-}}^8$ ${\mathit{S}}_{7/2}$ multiplet component, in agreement with a calculated 93% effect, taking into account the incomplete circular polarization of the photon beam and the experimental geometry. This is a very strong MCD effect and provides interesting perspectives for surface and thin-film magnetism, as well as a versatile sensor for circular polarization of soft x rays over a wide photon-energy range.