  We have investigated the effects of post growth low temperature annealing on
the magnetic, electrical and structural properties of
(Ga_0.94,Mn_0.06)(As_0.9,P_0.1) layers grown by molecular beam epitaxy. By
controlling the annealing time we are able to tune the magnetic anisotropy
between an easy axis in the plane for the as-grown samples, to an easy axis
perpendicular to the plane for fully annealed samples. The increase of the
carrier density, as a result of annealing, is found to be the primary reason
for the change in magnetic anisotropy, in qualitative agreement with
theoretical predictions.
