Doping induced metallization of a narrow gap insulator FeGa$_{3}$

Narrow gap semiconductors attract great interest owing to an unusual metallization process which remains poorly understood despite decades of extensive research [1]. Here, we report on the effects of hole doping on properties of a nonmagnetic semiconductor FeGa$_{3}$ with a band gap of 0.4 eV [2]. By means of electrical resistivity, magnetization and specific heat measurements performed on single crystals grown from gallium flux we have found that a substitution of Mn for Fe in Fe$_{\mathrm{1-x}}$Mn$_{\mathrm{x}}$Ga3 (0.005\textless\ x \textless\ 0.03) yields an insulating state at high temperatures with residual magnetic moments. With lowering temperature, resistivity deviates from an activation-type behavior and nearly saturates at T\textless 100 K. Finally, it drops by as much as two orders of magnitude at temperature of 6 K, indicating a metal-insulator transition. Magnetization measurements did not show magnetic order associated with the transition. When an external magnetic field is applied, the metal-insulator transition moves to lower temperatures and eventually the resistivity returns to the insulating-type behavior in fields higher then of 5 Tesla. \\[4pt] [1] M. Imada et al, Rev. Mod. Phys., 70, 1039 (1998)\\[0pt] [2] M. Arita et al., Phys. Rev. B 83, 245116 (2011); Y. Hadano et al., J. Phys. Soc. Jpn. 78, 013702 (2009)