Optical bandedge of diluted magnetic semiconductors: difference between II-VI and III-V-based DMSs

The crossover between an impurity band (IB) and a valence band (VB) regime as a function of the magnetic impurity concentration in models for diluted magnetic semiconductors (DMS) is studied systematically by taking into consideration the Coulomb attraction between the carriers and the magnetic impurities. The density of states and the ferromagnetic transition temperature of a Spin-Fermion model applied to DMS are evaluated using Dynamical Mean-Field Theory (DMFT) and Monte C...

The high-spectral-resolution spectroscopic studies of the energy gap evolution, supplemented with electronic, magnetic and structural characterization, show that the modification of the GaAs valence band caused by Mn incorporation occurs already for a very low Mn content, much lower than that required to support ferromagnetic spin - spin coupling in (Ga,Mn)As. Only for n-type (Ga,Mn)As with the Mn content below about 0.3% the Mn-related extended states are visible as a featur...

The detailed nature of electronic states mediating ferromagnetic coupling in dilute magnetic semiconductors, specifically (Ga,Mn)As, has been an issue of long debate. Two confronting models have been discussed emphasizing host band vs. impurity band carriers. Using angle resolved photoemission we are for the first time able to identify a highly dispersive Mn-induced energy band in (Ga,Mn)As. Our results show that the electronic structure of the (Ga,Mn)As system is significant...

The rapidly developing field of ferromagnetism in diluted magnetic semiconductors, where a semiconductor host is magnetically doped by transition metal impurities to produce a ferromagnetic semiconductor (e.g. Ga_{1-x}Mn_xAs with x ~ 1-10 %), is discussed with the emphasis on elucidating the physical mechanisms underlying the magnetic properties. Recent key developments are summarized with critical discussions of the roles of disorder, localization, band structure, defects, a...

Recent progress in understanding and controlling spintronic properties of (Ga,Mn)As and related compounds is contrasted to diverging experimental and theoretical results concerning the origin of high temperature ferromagnetism discovered in an ample class of magnetically doped wide-band-gap semiconductors.

Diluted magnetic semiconductors (DMS) are interesting because of the interplay between the electronic and magnetic subsystems. We describe selected magnetic properties of IV-VI diluted magnetic semiconductors, looking at the similarities and differences between magnetic properties of II-VI, IV-VI, and III-V DMS. We focus on the influence of the crystalline and electronic structure of the material on its magnetic properties, especially on the exchange interactions among magnet...

The magnetic properties and the electronic excitations of the new diluted magnetic semiconductor Ba$_{1-x}$K$_{x}$(Zn$_{1-y}$Mn$_{y}$)$_{2}$As$_{2}$ have been studied by x-ray magnetic circular dichroism (XMCD) and resonant inelastic x-ray scattering (RIXS) at the Mn $L_{2,3}$ edge. The sum rule analysis of the XMCD spectra yields the net spin moment of $0.45\mu_{\text{B}}$/Mn and the small orbital moment of $0.05\mu_{\text{B}}$/Mn. This indicates that the Mn atoms are in the...

Magnetic linear dichroism and birefringence in (Ga,Mn)As epitaxial layers is investigated by measuring the polarization plane rotation of reflected linearly polarized light when magnetization lies in the plane of the sample. We report on the spectral dependence of the rotation and ellipticity angles in a broad energy range of 0.12-2.7 eV for a series of optimized samples covering a wide range on Mn-dopings and Curie temperatures and find a clear blue shift of the dominant pea...

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 ...

We have performed ab initio calculations within the density-functional theory for Ga_{1-x}Mn_xAs diluted semiconductors. Total energy results unambiguously show that a quasi-localized down-spin hole, with strong p-like character, surrounds the fully polarized Mn up-spin d^5-electrons. Calculations indicate that the holes form an essentially dispersionless impurity band, thus rendering effective-mass descriptions of hole states open to challenge. We obtain estimates both for t...