Effects of random distribution of Mn,Fe in Co2Mn 1-xFexSi Heusler compounds probed by 55Mn nuclear magnetic resonance

Abstract

Recent spin echo nuclear magnetic resonance (NMR) revealed that the half-metallic Co2 Mn1-x Fex Si Heusler alloys exhibit the L 21 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 Mn55 nuclei, as this shell is the first magnetically active shell, leading to a line splitting in the Mn55 NMR spectra. A comparison, as presented in this paper, of all Mn55 NMR satellite lines shows that the resonance frequencies corresponding to the same number of Fe atoms in the third shell of Mn55 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. © 2008 American Institute of Physics.