Weak localization in Ga1-xMnxAs:: Evidence of impurity band transport

We report the observation of negative magnetoresistance in the ferromagnetic semiconductor Ga(1-x)Mn(x)As, x=0.05-0.08, at low temperatures (T < 3 K) and low magnetic fields (0 < B < 20 mT). We attribute this effect to weak localization. Observation of weak localization strongly suggests impurity band transport in these materials, since for valence band transport one expects either weak antilocalization due to strong spin-orbit interactions or total suppression of interference by intrinsic magnetization. In addition to the weak localization, we observe Altshuler-Aronov electron-electron interaction effects in this material.