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 $T<15$\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