Anomalous Hall effect from Berry curvature in Ga_1-xMn_xAs_1-yP_y films

While the carrier-mediated ferromagnetism in GaMnAs has been extensively studied in the past, the origin of anomalous Hall effect (AHE) in magnetic III-V systems remains elusive. It is also expected that the valence bands of III-Mn-V compounds exhibit a strong Berry curvature, possibly resulting from the strain effects that occur in GaMnAsP grown on GaAs and alter the shape of the valence band. In this work, we measure the AHE in a series of Ga_1−xMn_xAs_1−yP_y alloys grown by molecular beam epitaxy on GaAs (100) with varying amounts of P (up to 27%) and Mn (1.5%, 2.9% and 4.1%). Specifically, we carried out extensive measurements of transverse and longitudinal resistivity as a function of both magnetic field and temperature. We find that the Hall conductivity can be tuned by varying the phosphorus concentration y and the conductivity in the metallic regime.  Theoretical calculations are underway to relate this behavior to specific changes in the band dispersion of GaMnAsP.