Magneto-optical properties of (Ga,Mn)As: an ab--initio determination

The magneto-optical properties of (Ga,Mn)As have been determined within density functional theory using the highly precise full-potential linear augmented plane wave (FLAPW) method. A detailed investigation of the electronic and magnetic properties in connection to the magneto-optic effects is reported. The spectral features of the optical tensor in the 0-10 eV energy range are analyzed in terms of the band structure and density of states and the essential role of the dipole matrix elements is highlighted by means of Brillouin zone dissection. Using an explicit representation of the Kerr angle in terms of real and imaginary parts of the tensor components, a careful analysis of the Kerr spectra is also presented. The results of our study can be summarized as follows: i) different types of interband transitions do contribute in shaping the conductivity tensor; ii) the dipole matrix elements are important in obtaining the correct optical spectra; iii) different regions in the irreducible Brillouin zone contribute to the conductivity very differently; iv) a minimum in the Re $\sigma_{xx}$ spectra can give rise to a large Kerr rotation angle in the same energy region; and v) materials engineering via the magneto-optical Kerr effect is possible provided that the electronic structure of the material can be tuned in such a way as to \emph{enhance} the depth of the minima of Re $\sigma_{xx}$.