Mn-55 Nmr Study Of Quaternary Half-Metallic Ferromagnetic Co2mn1-Xfexsi Heusler Compounds

In this work, the Mn-55 spin-echo nuclear magnetic resonance technique is used to systematically analyze the complete substitutional series Co2Mn1-x Fe x Si in terms of the resonance frequencies of the satellite structure and the corresponding hyperfine fields of the Mn-55 nuclei. The frequency spacing between satellite lines is constant within a compound, but decreases with increasing Fe concentration x, which originates in changes in the band structure. These changes are also responsible for the altered resonance frequencies observed for the same third shell environment but corresponding to a different overall Fe concentration x. All modifications in the hyperfine field upon substitution of Mn by Fe can be uniquely assigned to an entirely random distribution of Mn and Fe limited to only one (4b) out of four fcc sublattices constituting the L2(1) Heusler structure, demonstrating that the complete substitutional series Co2Mn1-x Fe x Si is crystallographically very well defined. This very high degree of order sets the stage for the observation of stable half-metallic ferromagnetism which is typically very sensitive to the structural order.