5 research outputs found
Electronic structure and magnetic properties of metallocene multiple-decker sandwich nanowires
We present a study of the electronic and magnetic properties of the
multiple-decker sandwich nanowires () composed of cyclopentadienyl (CP)
rings and 3d transition metal atoms (M=Ti to Ni) using first-principles
techniques. We demonstrate using Density Functional Theory that structural
relaxation play an important role in determining the magnetic ground-state of
the system. Notably, the computed magnetic moment is zero in , while in
a significant turn-up in magnetic moment is evidenced. Two compounds
show a half-metallic ferromagnetic ground state with a gap within
minority/majority spin channel. In order to study the effect of electronic
correlations upon the half-metallic ground states in , we introduce a
simplified three-bands Hubbard model which is solved within the Variational
Cluster Approach. We discuss the results as a function of size of the reference
cluster and the strength of average Coulomb and exchange parameters.
Our results demonstrate that for the range of studied parameters and
the half-metallic character is not maintained in the presence of
local Coulomb interactions.Comment: 9 pages, 9 figures, submited to PR
Absence of halfmetallicity in defect-free Cr, Mn-delta-doped Digital Magnetic Heterostructures
We present results of a combined density functional and many-body
calculations for the electronic and magnetic properties of the defect-free
digital ferromagnetic heterostructures obtained by doping GaAs with Cr and Mn.
While local density approximation/(+U) predicts half-metallicity in these
defect-free delta-doped heterostructures, we demonstrate that local many-body
correlations captured by Dynamical Mean Field Theory induce within the minority
spin channel non-quasiparticle states just above . As a consequence of the
existence of these many-body states the half-metallic gap is closed and the
carriers spin polarization is significantly reduced. Below the Fermi level the
minority spin highest valence states are found to localize more on the GaAs
layers being independent of the type of electronic correlations considered.
Thus, our results confirm the confinement of carriers in these delta-doped
heterostructures, having a spin-polarization that follow a different
temperature dependence than magnetization. We suggest that polarized
hot-electron photoluminescence experiments might bring evidence for the
existence of many-body states within the minority spin channel and their finite
temperature behavior.Comment: 10 pages 8 figures, submitted to PR
Magnetism and electronic structure calculation of SmN
The results of the electronic structure calculations performed on SmN by
using the LDA+U method with and without including the spin-orbit coupling are
presented. Within the LDA+U approach, a N(2) band polarization of is induced by Sm(4)-N(2) hybridization, and a half-metallic
ground state is obtained. By including spin-orbit coupling the magnetic
structure was shown to be antiferromagnetic of type II, with Sm spin and
orbital moments nearly cancelling. This results into a semiconducting ground
state, which is in agreement with experimental results.Comment: Submitted to JPCM, 12 pages, 4 figure
Electronic correlations in short-period (CrAs)n/(GaAs)n ferromagnetic heterostructures
We investigate half-metallicity in [001] stacked (CrAs)/(GaAs)
heterostructures with by means of a combined many-body and
electronic structure calculation. Interface states in the presence of strong
electronic correlations are discussed for the case . For our
results indicate that the minority spin half-metallic gap is suppressed by
local correlations at finite temperatures, and continuously shrinks upon
increasing the heterostructure period. Although around room temperature the
magnetization of the heterostructure deviates by only from the ideal
integer value, finite temperature polarization at is reduced by at least
. Below the Fermi level the minority spin highest valence states are found
to localize more on the GaAs layers while lowest conduction states have a
many-body origin. Our results, therefore, suggest that in these
heterostructures holes and electrons remain separated among different layers.Comment: 9 pages, 12 pages, submitted to PR