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

We report on the magnetic and the electronic properties of the prototype dilute magnetic semiconductor Ga$_{1-x}$Mn$_x$As using infrared (IR) spectroscopy. Trends in the ferromagnetic transition temperature $T_C$ with respect to the IR spectral weight are examined using a sum-rule analysis of IR conductivity spectra. We find non-monotonic behavior of trends in $T_C$ with the spectral weight to effective Mn ratio, which suggest a strong double-exchange component to the FM mech...

We review the first decade of extensive optical studies of ferromagnetic, III-Mn-V diluted magnetic semiconductors. Mn introduces holes and local moments to the III-V host, which can result in carrier mediated ferromagnetism in these disordered semiconductors. Spectroscopic experiments provide direct access to the strength and nature of the exchange between holes and local moments; the degree of itineracy of the carriers; and the evolution of the states at the Fermi energy wi...

The dynamical behavior of the magnetism of diluted magnetic semiconductors (DMS) has been investigated by means of atomistic spin dynamics simulations. The conclusions drawn from the study are argued to be general for DMS systems in the low concentration limit, although all simulations are done for 5% Mn-doped GaAs with various concentrations of As antisite defects. The magnetization curve, $M(T)$, and the Curie temperature $T_C$ have been calculated, and are found to be in g...

We have investigated the electronic structure of the $p$-type diluted magnetic semiconductor In$_{1-x}$Mn$_x$As by photoemission spectroscopy. The Mn 3$d$ partial density of states is found to be basically similar to that of Ga$_{1-x}$Mn$_x$As. However, the impurity-band like states near the top of the valence band have not been observed by angle-resolved photoemission spectroscopy unlike Ga$_{1-x}$Mn$_x$As. This difference would explain the difference in transport, magneti...

Using spin-1/2 description of valence holes and Kondo coupling between local spins and carriers, GaAs-based III-V diluted magnetic semiconductors (DMS)are studied in the coherent potential approximation(CPA). Our calculated relation of ground-state energy and impurity magnetization shows that ferromagnetism is always favorable at low temperatures. For very weak Kondo coupling, the density of states (DOS) of the host semiconductor is not modified much. Impurity band can be g...

The muffin-tin model of an effective-mass electron interacting with magnetic ions in semiconductors is extended to incorporate electrostatic potentials that are present in the case of Mn-based III-V compounds (${Ga}_{1-x} {Mn}_x {N}$, ${Ga}_{1-x} {Mn}_x {As}$). Since the conduction band electron is repelled from negatively charged magnetic ions and attracted by compensating donors, the \emph{apparent} value of the s-d exchange coupling $N_0 \alpha$ is reduced. It is shown tha...

We present a theoretical study of diluted magnetic semiconductors that treats the local sp-d exchange interaction J between the itinerant carriers and the Mn d electrons within a realistic band structure and goes beyond previous mean-field approaches. In case of (Ga,Mn)As, we find that strong exchange potentials tightly bind carriers near impurity sites. Spin-orbit coupling is found to have a more pronounced effect on spin polarization at weak coupling and this feature can be...

The electronic and magnetic properties of a new diluted magnetic semiconductor (DMS) Ba$_{1-x}$K$_{x}$(Zn$_{1-y}$Mn$_{y}$)$_{2}$As$_{2}$, which is isostructural to so-called 122-type Fe-based superconductors, are investigated by x-ray absorption spectroscopy (XAS) and resonance photoemission spectroscopy (RPES). Mn $L_{2,3}$-edge XAS indicates that the doped Mn atoms have the valence 2+ and strongly hybridize with the $4p$ orbitals of the tetrahedrally coordinating As ligands...

(Ga,Mn)As is a paradigm diluted magnetic semiconductor which shows ferromagnetism induced by doped hole carriers. With a few controversial models emerged from numerous experimental and theoretical studies, the mechanism of the ferromagnetism in (Ga,Mn)As still remains a puzzling enigma. In this Letter, we use soft x-ray angle-resolved photoemission spectroscopy to positively identify the ferromagnetic Mn 3d-derived impurity band in (Ga,Mn)As. The band appears hybridized with ...

The properties of diluted Ga$_{1-x}$Mn$_x$As are calculated for a wide range of Mn concentrations within the local spin density approximation of density functional theory. M\"ulliken population analyses and orbital-resolved densities of states show that the configuration of Mn in GaAs is compatible with either 3d$^5$ or 3d$^6$, however the occupation is not integer due to the large $p$-$d$ hybridization between the Mn $d$ states and the valence band of GaAs. The spin splittin...