Electronic structures of amorphous M100-xZrx alloys (M = Fe, Co, Ni, Cu) studied using core-level x-ray photoemission spectroscopy

Abstract

The electronic structures of amorphous a-Fe100-xZrx and a-(Fe1-yMy)(33)Zr-67 alloys (M = Co, Ni, Cu) have been investigated by using x-ray photoemission spectroscopy. For a-Fe100-xZrx, the linewidths of both the Fe 2p and Zr 3d core-level spectra become narrower with increasing x. Systematic line-shape analysis reveals that such a trend could be either due to the decrease in the Auger recombination process or due to the decrease in the exchange splitting of corehole electrons. The broad Zr 3d spectrum for x = 10 is decomposed into two peaks, suggesting a localized nature of the Zr 4d electrons in a-Fe90Zr10. For a-(Fe1-yMy)(33)Zr-67 (M = Co, Ni), the Fe 2p spectrum becomes narrower and the shoulder-like satellite structure becomes more pronounced with increasing y, reflecting the increasingly localized nature of the Fe 3d electrons. In contrast, the M 2p spectra of a-(Fe1-yMy)(33)Zr-67 remain essentially unchanged with varying y, implying that the M 2p spectra of a-M100-xZrx are much less sensitive to the M ion species than to the fractional concentrations of M and Zr ions. As M varies from Fe to Co and Ni in a-M33Zr67, the Zr 3d spectrum exhibits a small shift toward higher binding energy and a slight increase in the linewidth. Band-structure calculations for ordered MZr2 (M = Fe, Co, Ni, Cu) predict that both the density of states at the Fermi level N(E-F) and the total number of valence electrons increase as M varies from Fe to Co and Ni, which is consistent with the measured Zr 3d spectra of a-M33Zr67.