  Electrical current manipulation of magnetization switching through
spin-orbital coupling in ferromagnetic semiconductor (Ga,Mn)As Hall bar devices
has been investigated. The efficiency of the current-controlled magnetization
switching is found to be sensitive to the orientation of the current with
respect to the crystalline axes. The dependence of the spin-orbit effective
magnetic field on the direction and magnitude of the current is determined from
the shifts in the magnetization switching angle. We find that the strain
induced effective magnetic field is about three times as large as the Rashba
induced magnetic field in our GaMnAs devices.
