Local moments in Mn-based Heusler alloys and their electronic structures

Abstract

In this article we present a detailed study of the electronic structure from various Mn-based Heusler alloys using x-ray photoelectron spectroscopy (XPS) and x-ray emission spectroscopy (XES) techniques. Performing the measurements on the Mn-$2p$ core levels as well as on the valence-band states we arrive at a more or less complete description of the electronic and magnetic properties of these compounds. The experimental Mn-$2p$ spectra have been compared with fully relativistic photoemission calculations, which are based on the solution of the spin-polarized Dirac equation. The almost constant exchange splitting of about 0.35 eV, measured between the different Mn-$2p$ sublevels is explainable in terms of the local magnetic moment at the Mn site. Moreover a strong relationship between the magnetization direction and the line shapes of the calculated Mn-$2p$ core-level spectra has been revealed from our analysis. Depending on the atomic number of the Z element we obtain from XES experiments an increasing localization of the Mn-$3d$ states. Also the interatomic distances in the different alloys seem to play an important rule in this process. To support this result we performed in addition valence-band measurements by applying XP. These data, which agree very well with the corresponding x-ray emission spectra are quantitatively reproduced from first-principle electronic structure calculations.