36 research outputs found
Resonant electronic states and I-V curves of Fe/MgO/Fe(100) tunnel junctions
The bias dependence of the tunnel magnetoresistance (TMR) of Fe/MgO/Fe tunnel
junctions is investigated theoretically with a fully self-consistent scheme
that combines the non-equilibrium Green's functions method with density
functional theory. At voltages smaller than 20 mVolt the I-V characteristics
and the TMR are dominated by resonant transport through narrow interface states
in the minority spin-band. In the parallel configuration this contribution is
quenched by a voltage comparable to the energy width of the interface state,
whereas it persists at all voltages in the anti-parallel configuration. At
higher bias the transport is mainly determined by the relative positions of the
band-edges in the two Fe electrodes, which causes a decrease of the
TMR
Interaction of spherical nanoparticles with a highly focused beam of light
The interaction of a highly focused beam of light with spherical nanoparticles is investigated for linear and radial polarizations. An analytical solution is obtained to calculate this interaction. The Richards-Wolf theory is used to express the incident electric field near the focus of an aplanatic lens. The incident beam is expressed as an integral where the integrand is separated into transverse-electric (TE) and transverse-magnetic (TM) waves. The interaction of each TE and TM wave with a spherical nanoparticle is calculated using the Mie theory. The resulting analytical solution is then obtained by integrating the scattered waves over the entire angular spectrum. A finite element method solution is also obtained for comparison
Role of Coulomb correlation on magnetic and transport properties of doped manganites: La0.5Sr0.5MnO3 and LaSr2Mn2O7
Results of LSDA and LSDA+U calculations of the electronic structure and
magnetic configurations of the 50% hole-doped pseudocubic perovskite
La0.5Sr0.5MnO3 and double layered LaSr2Mn2O7 are presented. We demonstrate that
the on-site Coulomb correlation (U) of Mn d electrons has a very different
influence on the (i) band formations, (ii) magnetic ground states, (iii)
interlayer exchange interactions, and (iv) anisotropy of the electrical
transport in these two manganites. A possible reason why the LSDA failures in
predicting observed magnetic and transport properties of the double layered
compound - in contrast to the doped perovskite manganite - is considered on the
basis of a p-d hybridization analysis.Comment: 11 pages, 3 figure
Interface characterization of Co2MnGe/Rh2CuSn Heusler multilayers
All-Heusler multilayer structures have been investigated by means of high
kinetic x-ray photoelectron spectroscopy and x-ray magnetic circular dichroism,
aiming to address the amount of disorder and interface diffusion induced by
annealing of the multilayer structure. The studied multilayers consist of
ferromagnetic CoMnGe and non-magnetic RhCuSn layers with varying
thicknesses. We find that diffusion begins already at comparably low
temperatures between 200 C and 250 C, where Mn appears to
be most prone to diffusion. We also find evidence for a 4 {\AA} thick
magnetically dead layer that, together with the identified interlayer
diffusion, are likely reasons for the small magnetoresistance found for
current-perpendicular-to-plane giant magneto-resistance devices based on this
all-Heusler system