28 research outputs found
Percolation in Models of Thin Film Depositions
We have studied the percolation behaviour of deposits for different
(2+1)-dimensional models of surface layer formation. The mixed model of
deposition was used, where particles were deposited selectively according to
the random (RD) and ballistic (BD) deposition rules. In the mixed one-component
models with deposition of only conducting particles, the mean height of the
percolation layer (measured in monolayers) grows continuously from 0.89832 for
the pure RD model to 2.605 for the pure RD model, but the percolation
transition belong to the same universality class, as in the 2- dimensional
random percolation problem. In two- component models with deposition of
conducting and isolating particles, the percolation layer height approaches
infinity as concentration of the isolating particles becomes higher than some
critical value. The crossover from 2d to 3d percolation was observed with
increase of the percolation layer height.Comment: 4 pages, 5 figure
Electronic transport through domain walls in ferromagnetic nanowires: Co-existence of adiabatic and non-adiabatic spin dynamics
We study the effect of a domain wall on the electronic transport in
ferromagnetic quantum wires. Due to the transverse confinement, conduction
channels arise. In the presence of a domain wall, spin up and spin down
electrons in these channels become coupled. For very short domain walls or at
high longitudinal kinetic energy, this coupling is weak, leads to very few spin
flips, and a perturbative treatment is possible. For very long domain wall
structures, the spin follows adiabatically the local magnetization orientation,
suppressing the effect of the domain wall on the total transmission, but
reversing the spin of the electrons. In the intermediate regime, we numerically
investigate the spin-dependent transport behavior for different shapes of the
domain wall. We find that the knowledge of the precise shape of the domain wall
is not crucial for determining the qualitative behavior. For parameters
appropriate for experiments, electrons with low longitudinal energy are
transmitted adiabatically while the electrons at high longitudinal energy are
essentially unaffected by the domain wall. Taking this co-existence of
different regimes into account is important for the understanding of recent
experiments.Comment: 10 pages, 6 figure
Domain wall resistance in
The clear separation of the domain wall magnetoresistance from the
anisotropic magnetoresistance has been successfully achieved by
investigating the transversal magnetoresistance of individual
\chem{(Co/Pt)_{10}}-nanowires. Since the magnetic easy axis of
this nanowires is out of plane, the magnetization is always
perpendicular to the current direction when applying a magnetic
field transversally. Most importantly, even the domain walls do
not give rise to an anisotropic resistance contribution by
themselves under these conditions, and thus the pure domain wall
magnetoresistance can be measured. The interpretation of the
resistance behavior is confirmed by Monte Carlo simulations giving
the magnetization distribution during the magnetization reversal
process. It can be shown that the observed resistance behavior
reflects the dependence of the domain wall magnetoresistance on
the domain wall structure
Absence of weak electron localization in ferromagnetic cobalt wires
We have investigated the low-temperature resistance behavior and
the magnetoresistance of single-domain cobalt wires of
400\un{\mu m} length, 2\un{\mu m} width and thicknesses
between 5\un{nm} and 32\un{nm}. A logarithmic resistance increase
is observed for temperatures \un{K} which is consistently
explained as originating from enhanced electron-electron
interactions (EEI) in two dimensions rather than from weak
electron localization (WEL). The results are confirmed for both
platinum-capped and un-capped cobalt wires of various thicknesses.
Our experimental results are compared with recent theoretical
predictions for 2-dimensional ferromagnetic systems
IN-SITU RHEED AND STM INVESTIGATIONS ON THE EPITAXIAL GROWTH OF FE/PD MULTILAYERS ON PD(001)-BUFFERED SAPPHIRE
We present the preparation of (001) oriented (Fe/Pd) multilayer films on sapphire substrates. The samples are grown on specifically prepared Pd buffer layers, which are pre-seeded with a thin Fe layer. Structural and topographical investigations utilizing in-situ RHEED and STM and ex-situ XRD clearly evidence epitaxial growth along the [001] direction throughout more than 30 Fe/Pd bilayers
µSR STUDY OF Fe1-xNix INVAR ALLOY
Zero and transverse-field µSR has been measured on fcc Fe66Ni34 Invar alloy. The hyperfine coupling is obtained Ahf ~ -2.4 kG/µB. The muon spin relaxation rate above Tc follows 1 / Tµ = 2.2 / (T - Tc) (µs)-1. These facts seem microscopically consistent with the deviation from the Slater-Pauling curve and the reduction of the local moment