Chemical potential shift ofFe3−xVxSistudied by hard x-ray photoemission

Abstract

Core-level photoemission spectra of ${\text{Fe}}_{3\ensuremath{-}x}{\text{V}}_{x}\text{Si}$ alloys with inequivalent ${\text{Fe}}_{\text{I}}$ and ${\text{Fe}}_{\text{II}}$ sites are investigated via hard x-ray photoemission spectroscopy over the entire doping range $x=0--1$. All the measured $1s$ core-level peaks are found to shift to higher binding energy with increasing V concentration. First-principles, all electron charge- and spin-self-consistent electronic structure computations within the framework of the local-spin-density approximation are used to interpret the experimental results. The measured size of energy shift in going from $x=0$ to 1 is consistent with the corresponding theoretical value for the ${\text{Fe}}_{\text{II}}$ and $\text{Si}\text{ }1s$ core levels, whereas for the ${\text{Fe}}_{\text{I}}$ and V core levels the computed shifts are generally larger than the experimental values. We ascribe these discrepancies to the effects of the core-hole screening in the final state which are not accounted for in the computations. In a rigid-band model the chemical potential and the core-level binding energies are expected to decrease with V doping as electrons are depleted from the Fermi energy. The observed increase in the binding energy of core levels thus supports a picture of the electronic structure where V doping induces a ``pseudogap'' or a region of reduced density of states in the vicinity of the Fermi energy.