Effect of Electron-Deficient Substitution on the Spin Dynamics in FeGa3

The nuclear quadrupole resonance study of the electron-deficient substitution in the promising thermoelectric material FeGa₃ resulting in the poorly studied Fe_0.92Re_0.08Ga₃ and Fe_0.92Mn_0.08Ga₃ compounds has been carried out. The doping of compounds of this structure type promotes the study of the dependence of the thermoelectric characteristics on the electronic structure and finally makes it possible to increase the thermoelectric efficiency, which is very important for applications. Both compounds exhibit pronounced signatures of the formation of an additional acceptor band inside the main band gap, which is determined by rhenium and manganese substituent atoms. Nuclear quadrupole resonance spectra, as well as nuclear spin–lattice relaxation and its temperature evolution, are significantly different for the compounds under study. This difference is due to different statistical distributions of substituent atoms (predominant formation of homo- and heterogeneous dumbbells in the rhenium- and manganese-substituted compounds, respectively) caused by their outer electron shells.