We report the observation of negative magnetoresistance in the ferromagnetic semiconductor GaMnAs 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 provides a strong evidence of impurity band transport in these materials, since for valence band transport one expects either weak anti-localization 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 interactions effect in this material.
@article{arxiv.0707.2416,
title = {Weak localization in GaMnAs: evidence of impurity band transport},
author = {L. P. Rokhinson and Y. Lyanda-Geller and Z. Ge and S. Shen and X. Liu and M. Dobrowolska and J. K. Furdyna},
journal= {arXiv preprint arXiv:0707.2416},
year = {2009}
}