Electronic structure and magnetic and hyperfine properties of Fe/V sandwiches and interfaces.

Abstract

The electronic, magnetic, and hyperfine properties of 15-atom clusters of Fe/V superstructures are calculated using the first-principles discrete-variational X\ensuremath{\alpha} method (DV-X\ensuremath{\alpha}). The superstructures include a monolayer of Fe sandwiched between two thick V layers, an Fe/V interface, and a single layer of Fe on bulk V. The numbers of V atoms in the first and second shells surrounding the central Fe atom (N and M, respectively) were varied and the trends exhibited by the electronic magnetic moments, \ensuremath{\mu}, hyperfine fields, ${H}_{c}$, isomer shifts, IS, and the electric quadrupole splitting, ${\ensuremath{\Delta}}_{\mathrm{EQ}}$, were investigated. The results show that the magnetic moment on the central Fe atom does not decrease with increasing N contrary to previous interpretations of experimental results. The dependence of the central atom magnetic moment on M is minor. The magnetic hyperfine field decreases in magnitude with increasing N and almost vanishes when N=8. The 3d partial electronic density of states reflects asymmetry in the bonding between the spin-up and the spin-down states of Fe and V and the asymmetry becomes more pronounced with increasing N. The isomer shift of Fe/V systems relative to \ensuremath{\alpha}-Fe becomes more negative as N increases. A linear correlation of the average ${H}_{c}$ and IS is found and its slope determined. It is indicated that this slope could be used to determine \ensuremath{\alpha}, the isomer-shift calibration constant. The electric quadrupole splitting ${\ensuremath{\Delta}}_{\mathrm{EQ}}$ shows no regular trends. A model is proposed to explain the above trends.