Effect of light illumination on the [100] uniaxial magnetic anisotropy of GaMnAs film

• Light illumination changes the magnetic anisotropies of GaMnAs films.
• Dramatic change occurred in the uniaxial anisotropy along the [100] direction.
• The effect must be related to the variation of the carrier density and to the structural change due to the annealing by light illumination.

The effect of light illumination on the magnetic anisotropy of GaMnAs has been investigated by using the planar Hall effect measurement. In as-grown GaMnAs, typical types of magnetic anisotropies, cubic crystalline anisotropy along the 〈100〉 directions and uniaxial anisotropy along the [110] direction, were clearly observed in the planar Hall resistance (PHR) measurements. The behavior of the PHR, however, changed after light illumination by showing significant asymmetry between the [100] and the [010] directions, which was explained by the appearance (or enhancement) of a new type of uniaxial anisotropy along the [100] direction in the film. The experiment reveals that light illumination can significantly alter the magnetic anisotropies of the GaMnAs film by changing the magnitude of existing anisotropies as well as inducing anisotropy along the [100] direction.