RESUMO
We report a study of the electronic properties of the ferromagnetic semiconductor (Ga,Mn)As using magnetic linear dichroism in the angular dependence of Mn 2p photoemission under hard x-ray excitation. Bulk plasmon loss satellites demonstrate that the probed Mn ions are incorporated deep within the GaAs lattice, while the observed large dichroism indicates that the spectra originate from ferromagnetic substitutional Mn. Simulations of the spectra using an Anderson impurity model show that the ferromagnetic Mn 3d electrons of substitutional Mn in (Ga,Mn)As are intermediate between localized and delocalized.
RESUMO
Remarkably anisotropic Mn L2,3 x-ray magnetic circular dichroism spectra from the ferromagnetic semiconductor (Ga,Mn)As are reported. States with cubic and uniaxial symmetry are distinguished by careful analysis of the angle dependence of the spectra. The multiplet structures with cubic symmetry are qualitatively reproduced by calculations for an atomiclike d5 configuration in tetrahedral environment, and show zero anisotropy in the orbital and spin moments within the experimental uncertainty. However, hybridization with the host valence bands is reflected by the presence of a preedge feature with a uniaxial anisotropy and a marked dependence on the hole density.
RESUMO
We present a combined theoretical and experimental study of the ferromagnetic semiconductor (Ga,Mn)As which explains the remarkably large changes observed on low-temperature annealing. Careful control of the annealing conditions allows us to obtain samples with ferromagnetic transition temperatures up to 159 K. Ab initio calculations, in situ Auger spectroscopy, and resistivity measurements during annealing show that the observed changes are due to out diffusion of Mn interstitials towards the surface, governed by an energy barrier of 0.7-0.8 eV. Electric fields induced by Mn acceptors have a significant effect on the diffusion.