Effects of random distribution of Mn,Fe in Co2Mn1-xFexSi Heusler compounds probed by 55Mn nuclear magnetic resonance

Recent spin echo nuclear magnetic resonance (NMR) revealed that the half-metallic Co2Mn1-xFexSi Heusler alloys exhibit the L21 structure with random distribution of Mn and Fe on the 4b Wyckoff position. This random distribution is most prominent in the third coordination shell of the 55Mn nuclei, as this shell is the first magnetically active shell, leading to a line splitting in the 55Mn NMR spectra. A comparison, as presented in this paper, of all 55Mn NMR satellite lines shows that the resonance frequencies corresponding to the same number of Fe atoms in the third shell of 55Mn shift to slightly different resonance frequencies with increasing overall Fe content x. This shift is related to the constructive contribution of higher shells to the hyperfine field. These higher shells affect also the satellite linewidth, leading to a parabolic behavior with increasing Fe concentration x. This parabolic behavior is modified by the frequency spacing related to the replacement of Mn by Fe.