Physical properties of FeGa$_2$Se$_4$ under an applied alternating current

The temperature and frequency dependences of the permittivity and conductivity of FeGa$_2$Se$_4$ crystals under an applied alternating current are investigated. The values of the permittivity are determined. It is assumed that an increase in $\varepsilon'$ is related to an increase in the defect concentration with temperature. It is established that the regularity $\sigma\propto f^S$ (0.1 $\le S\le$ 1.0) is fulfilled for conductivity in the temperature range of 294–374 K at frequencies of 10$^4$–2 $\times$ 10$^5$ Hz. In the FeGa$_2$Se$_4$ crystal, the variation in the frequency dependence of the conductivity can be explained as follows: there are the clusters in crystals containing localized states with almost identical energy, and the electron hopping occurs between them. In the FeGa$_2$Se$_4$ compound, the conductivity is characterized by band-hopping mechanisms.