Electron Localization in a Magnetic Semiconductor: ${\mathrm{Gd}}_{3-x}{\nu }_x{\mathrm{S}}_4$

The metal-insulator transition in the magnetic semiconductor ${\mathrm{Gd}}_{3-x}{v}_x{\mathrm{S}}_4$, where $v$ stands for vacancies, has been studied by tuning through the transition with the application of a magnetic field at low temperatures. For two samples with $x=0.321\mathrm{} \mathrm{and} 0.325$ the transition is continuous. $\sigma (T\to 0)$ is linear in $H-H_c$ which implies that $\sigma (T\to 0)\propto (E-E_c)$, where $H_c$ is a critical field and $E_c$ is the mobility edge. This is consistent with new scaling theories of both localization and interaction effects.