Magnetoelectric properties of oxygenated (Ga,Mn)As

The effect of oxygen plasma exposure on the magnetoelectrical properties of (Ga,Mn)As films is investigated. A significant increase in the oxygen content of the plasma-treated (Ga,Mn)As is visible in depth-profile x-ray photoelectron spectroscopy. The temperature dependence of the electrical resistance shows that after oxygenation the (Ga,Mn)As films become more resistive and that the distinct peak accounting for the Curie temperature shifts to lower temperatures. In addition, larger coercive fields for all in-plane directions are observed in the magnetoresistance signal after the treatment. X-ray absorption spectroscopy evidences the preservation of the electronic d5 state of the Mn atoms after oxygenation. This indicates that the changes in the electrical and consequently in the magnetic properties occur via a hole compensation mechanism promoted by the oxygen species incorporated during the plasma exposure.