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The interplay between disorder and spin polarization in a GaMnAs thin layer results into spin-polarized impurity hole bands. A figure of merit is defined to label the hole state as being extended or localized. The calculation leads to a phase diagram determining the metallic or non-metallic character of the sample. It is shown that samples with the highest figures of merit have a ratio between the extended hole density and the Mn concentration near 0.2, in agreement with the ratio of 0.1-0.25 known to occur among samples produced with the highest Curie temperatures. Both the non-metal-to-metal and the metal-to-non-metal transitions experimentally observed in the ferromagnetic regime are obtained, as the Mn concentration increases. An explanation is given for the occurrence of a maximal Curie temperature in ferromagnetic GaMnAs samples.
Formation of MnAs quantum dots in a regular ring-like distribution has been found on MBE-grown (GaMn)As surfaces after low-temperature annealing under As capping. The Mn was supplied by out-diffusing Mn interstitials from (GaMn)As. With 5 at% substit
Ultrafast two-color pump-probe measurements, involving coherent acoustic phonon (CAP) waves, have provided information simultaneously on the mechanical properties and on the electronic structure of ferromagnetic GaMnAs. The elastic constant C11 of Ga
The resistivity, temperature, and magnetic field dependence of the anomalous Hall effect in a series of metallic Ga1-xMnxAs thin films with 0.015=<x=<0.08 is presented. A quadratic dependence of the anomalous Hall resistance on the resistivity is obs
We consider the electronic properties of ferromagnetic bulk GaMnAs at zero temperature using two realistic tight-binding models, one due to Tang and Flatte and one due to Masek. In particular, we study the density of states, the Fermi energy, the inv
We provide experimental evidence that the upper limit of ~110 K commonly observed for the Curie temperature T_C of Ga(1-x)Mn(x)As is caused by the Fermi-level-induced hole saturation. Ion channeling, electrical and magnetization measurements on a ser