X-ray absorption studies of Al–Mn system

Abstract

X-ray K-absorption studies have been carried out on Al–Mn system comprising Al90Mn10, Al88Mn12, Al86Mn14, Al84Mn16, Al82Mn18 and Al81Mn19 samples. These samples have been characterized by x-ray diffraction (XRD) studies which support the formation of icosahedral phase. The x-ray K-absorption discontinuities in case of the Al–Mn system have been found to be shifted towards the high energy side with respect to the K-absorption edge of pure metal Mn, which indicates the behaviour of manganese atom as the cation. The x-ray absorption chemical shifts suggest a covalent bonding. The studies also indicate that with the increase in Mn concentration chemical shifts also increase.We have attempted to correlate the values of the electron to atom ratio (e/a) with the chemical shifts (ΔE). The nature of relationship between e/a and ΔE is quite similar to that between ΔE and Mn concentration. Further, we have estimated the density of states at the Fermi level D(EF) for these samples and plotted them against chemical shift values. Extrapolation from this graph between D(EF) and ΔE indicates a D(EF) value for Al metal which is quite near to the actual value for Al metal. These studies establish the existence of a pseudo gap in the case of presently investigated Al–Mn samples. The present studies also support our assumption of assigning the chemical shift values to the Fermi level in the case of Al–Mn system under present investigation.