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Zusammenfassung:
This paper reports on the bulk properties of the quaternary Heusler
alloy Co2Mn1-xFexSi with the Fe concentration x=0,1/2,1. All samples,
which were prepared by arc melting, exhibit L2(1) long-range order over
the complete range of Fe concentration. The structural and magnetic
properties of the Co2Mn1-xFexSi Heusler alloys were investigated by
means of x-ray diffraction, high- and low-temperature magnetometry,
Mossbauer spectroscopy, and differential scanning calorimetry. The
electronic structure was explored by means of high-energy photoemission
spectroscopy at about 8 keV photon energy. This ensures true bulk
sensitivity of the measurements. The magnetization of the Fe-doped
Heusler alloys is in agreement with the values of the magnetic moments
expected for a Slater-Pauling-like behavior of half-metallic
ferromagnets. The experimental findings are discussed on the basis of
self-consistent calculations of the electronic and magnetic structure.
To achieve good agreement with experiment, the calculations indicate
that on-site electron-electron correlation must be taken into account,
even at low Fe concentration. The present investigation focuses on
searching for the quaternary compound where the half-metallic behavior
is stable against outside influences. Overall, the results suggest that
the best candidate may be found at an iron concentration of about 50%.
