NMR and Mössbauer study of spin dynamics and electronic structure of Fe2+xV1-xAl and Fe2VGa
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In order to assess the magnetic ordering process in Fe2VAl and the related material Fe2VGa, we have carried out nuclear magnetic resonance (NMR) and Mössbauer studies. 27Al NMR relaxation measurements covered the temperature range 4–500 K in Fe2+xV1−xAl samples. We found a peak in the NMR spin-lattice relaxation rate, 27(T−11), corresponding to the magnetic transitions in each of these samples. These peaks appear at 125 K, 17 K, and 165 K for x=0.10, 0, and -0.05, respectively, and we connect these features with critical slowing down of the localized antisite defects. Mössbauer measurements for Fe2VAl and Fe2VGa showed lines with no hyperfine splitting, and isomer shifts nearly identical to those of the corresponding sites in Fe3Al and Fe3Ga, respectively. We show that a model in which local band filling leads to magnetic regions in the samples, in addition to the localized antisite defects, can account for the observed magnetic ordering behavior.