Effect of thermal annealing on the magnetic anisotropy of GaMnAs ferromagnetic semiconductor

• We have investigated the effect of thermal annealing on the magnetic anisotropies of a GaMnAs film.
• The cubic anisotropy decreased while the uniaxial anisotropy increased in the annealed samples.
• The direction of uniaxial anisotropy was changed between the [110] and the [11¯0] directions depending on the annealing condition.
• An additional uniaxial anisotropy along the [010] direction changed to the [100] direction with thermal annealing.
• The magnetic anisotropy of the GaMnAs film can be controlled by an appropriate thermal annealing process.

We have systematically investigated the influence of annealing on the magnetic anisotropy properties of GaMnAs film using an epilayer with a Mn concentration of 6.2%. The GaMnAs epilayer was grown by molecular beam epitaxy and the planar Hall effect measurement was used to monitor the magnetic anisotropy of the film. We found significant annealing-induced changes in the magnetic anisotropy properties of the GaMnAs film that depended on the annealing conditions. For example, the cubic anisotropy that gave a four-fold symmetry of magnetic easy axes decreased while the uniaxial anisotropy that gave a two-fold symmetry of magnetic easy axes increases in the samples annealed temperature below 300 °C. In particular, the uniaxial anisotropy along the [010] direction in as-grown GaMnAs film changed to the [100] direction by rotating by 90° after the sample was annealed at 300 °C for 3 h. This investigation thus indicates that the magnitude and the direction of the magnetic anisotropy in the GaMnAs film can be effectively controlled by choosing an appropriate annealing time and temperature.