Properties of the quaternary half-metal-type Heusler alloy Co₂Mn_1-xFe_xSi

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%