AIP Digital Archive
The spin-resolved density of states (DOS) of the Fe-based ferromagnetic metallic glasses Fe82B12Si6, Fe60Ni20B20, and Fe44Ni37B19 have been determined by spin-polarized photoemission spectroscopy (HeI, hv=21.2 eV, ΔE=100 meV). For the Fe82 sample the maximum of the up-spin DOS is located around 1.1 eV below EF, while the down-spin intensity has its maximum at EF indicating that the maximum of the down-spin DOS is above EF. This shows that the double-peak structure, which has been observed before in conventional photoemission, is due to ferromagnetic exchange splitting. The spin polarization at EF is slightly negative (−5%) and it has a maximum (+45%) at 2-eV binding energy, indicating the bottom of the down-spin Fe 3d states. A minimum in the spin polarization at about 5-eV binding energy corresponds to emission of unpolarized electrons from B 2p and Si 2p states. With increasing Ni concentration the maximum of the DOS shifts to higher binding energy, indicating the filling of the 3d states. The maximum of the polarization decreases and the spin polarization at EF becomes more negative (−8% for Fe60, −15 for Fe44−). No unambiguous "exchange splitting'' can be extracted from the spin-resolved energy distribution curves. There is no evidence for strong ferromagnetism, i.e., that the majority states are completely filled and below EF. The data indicate that neither the rigid band model nor the split-band model apply, but that there is a strong hybridization between the Fe 3d and Ni 3d states (common-band regime). Upon oxygen adsorption on the Fe82 sample the intensity of the metallic 3d states decreases (25% for 16 L exposure) and an unpolarized peak due to oxygen 2p grows at 5.5-eV binding energy. The spin polarization of the Fe 3d states is only slightly affected, ruling out the existence of oxygen-induced magnetically "dead layers.''
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