NMR and Mossbauer study of spin dynamics and electronic structure of Fe{2+x}V{1-x}Al and Fe2VGa

TL;DR

This study uses NMR and Mossbauer spectroscopy to investigate the magnetic ordering and electronic structure of Fe2VAl and Fe2VGa, revealing critical slowing down of antisite defects and local band filling effects.

Contribution

It provides new insights into the magnetic transition mechanisms in Fe2VAl and Fe2VGa through combined NMR and Mossbauer analyses, highlighting the role of antisite defects and local band filling.

Findings

Peaks in NMR relaxation rates at specific temperatures indicate magnetic transitions.

Mossbauer spectra show no hyperfine splitting, consistent with non-magnetic or weakly magnetic states.

A model involving local band filling explains the magnetic behavior observed.

Abstract

In order to assess the magnetic ordering process in Fe2VAl and the related material Fe2VGa, we have carried out nuclear magnetic resonance (NMR) and Mossbauer studies. 27Al NMR relaxation measurements covered the temperature range 4 -- 500 K in Fe(2+x)V(1-x)Al samples. We found a peak in the NMR spin-lattice relaxation rate, 27T1^-1, 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. Mossbauer 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.