85 research outputs found
Relation of Curie temperature and conductivity: (Ga,Mn)As alloy as a case study
Experimental investigations of diluted magnetic semiconductors indicate a
strong relation between Curie temperature and conductivity. Both quantities
depend non trivially on the concentration of magnetic impurities, the carrier
density, and the presence of compensating defects. We calculate both Curie
temperature and conductivity of (Ga,Mn)As alloys in a selfconsistent manner
based on the same first principles Hamiltonian in which the presence of
compensating defects is taken into account. The effect of As-antisites and
Mn-interstitials is determined separately and a good agreement between theory
and experiment exists only in the case where the dominating mechanism of is due
to the Mn-interstitials.Comment: The manuscript is accepted for publication in AP
On the origin of temperature dependence of interlayer exchange coupling in metallic trilayers
We study the influence of collective magnetic excitations on the interlayer
exchange coupling (IEC) in metallic multilayers. The results are compared to
other models that explain the temperature dependence of the IEC by mechanisms
within the spacer or at the interfaces of the multilayers. As a main result we
find that the reduction of the IEC with temperature shows practically the same
functional dendence in all models. On the other hand the influence of the
spacer thickness, the magnetic material, and an external field are quite
different. Based on these considerations we propose experiments, that are able
to determine the dominating mechanism that reduces the IEC at finite
temperatures.Comment: 8 pages, 7 figures, accepted for PR
Correlated Doping in Semiconductors: The Role of Donors in III-V Diluted Magnetic Semiconductors
We investigate the compositional dependence of the total energy of the mixed
crystals (Ga,Mn)As co-doped with As, Sn, and Zn. Using the ab initio LMTO-CPA
method we find a correlation between the incorporation of acceptors (Mn, Zn)
and donors (Sn, antisite As). In particular, the formation energy of As_Ga is
reduced by approx. 0.1 eV in the presence of Mn, and vice versa. This leads to
the self-compensating behavior of (Ga,Mn)As.Comment: 8 pages, 2 figures, presented at the XXXI Int. School of
Semiconducting Compounds, Jaszowiec 2002, Polan
Magnetoresistance of a semiconducting magnetic wire with domain wall
We investigate theoretically the influence of the spin-orbit interaction of
Rashba type on the magnetoresistance of a semiconducting ferromagnetic
nanostructure with a laterally constrained domain wall. The domain wall is
assumed sharp (on the scale of the Fermi wave length of the charge carriers).
It is shown that the magnetoresistance in such a case can be considerably
large, which is in a qualitative agreement with recent experimental
observations. It is also shown that spin-orbit interaction may result in an
increase of the magnetoresistance. The role of localization corrections is also
briefly discussed.Comment: 5 pages, 2 figure
Optical conductivity of Mn doped GaAs
We study the optical conductivity in the III-V diluted magnetic semiconductor
GaMnAs and compare our calculations to available experimental data. Our model
study is able to reproduce both qualitatively and quantitatively the observed
measurements. We show that compensation (low carrier density) leads, in
agreement to the observed measurements to a red shift of the broad peak located
at approximately 200 meV for the optimally annealed sample. The non
perturbative treatment appears to be essential, otherwise a blueshift and an
incorrect amplitude would be obtained. By calculating the Drude weight (order
parameter) we establish the metal-insulator phase diagram. We indeed find that
Mn doped GaAs is close to the metal-insulator transition and that for 5 and
7 doped samples, 20 of the carriers only are delocalized. We have found
that the optical mass is approximately 2 m. We have also interesting
results for overdoped samples which could be experimentally realized by Zn
codoping.Comment: the manuscript has been extended, new figures are include
Tunneling of Bloch electrons through vacuum barrier
Tunneling of Bloch electrons through a vacuum barrier introduces new physical
effects in comparison with the textbook case of free (plane wave) electrons.
For the latter, the exponential decay rate in the vacuum is minimal for
electrons with the parallel component of momentum , and
the prefactor is defined by the electron momentum component in the normal to
the surface direction. However, the decay rate of Bloch electrons may be
minimal at an arbitrary (``hot spots''), and the prefactor
is determined by the electron's group velocity, rather than by its
quasimomentum.Comment: 4 pages, no fig
- …