100 research outputs found
Fabrication of FeSi and Fe3Si compounds by electron beam induced mixing of [Fe/Si]2 and [Fe3/Si]2 multilayers grown by focused electron beam induced deposition
Fe-Si binary compounds have been fabricated by focused electron beam induced
deposition by the alternating use of iron pentacarbonyl, Fe(CO)5, and
neopentasilane, Si5H12 as precursor gases. The fabrication procedure consisted
in preparing multilayer structures which were treated by low-energy electron
irradiation and annealing to induce atomic species intermixing. In this way we
are able to fabricate FeSi and Fe3Si binary compounds from [Fe=Si]2 and
[Fe3=Si]2 multilayers, as shown by transmission electron microscopy
investigations. This fabrication procedure is useful to obtain nanostructured
binary alloys from precursors which compete for adsorption sites during growth
and, therefore, cannot be used simultaneously
Influence of the substrate-induced strain and irradiation disorder on the Peierls transition in TTF-TCNQ microdomains
The influence of the combined effects of substrate-induced strain, finite
size and electron irradiation-induced defects have been studied on individual
micron-sized domains of the organic charge transfer compound
tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) by temperature-dependent
conductivity and current-voltage measurements. The individual domains have been
isolated by focused ion beam etching and electrically contacted by focused ion
and electron beam induced deposition of metallic contacts. The
temperature-dependent conductivity follows a variable range hopping behavior
which shows a crossover of the exponent as the Peierls transition is
approached. The low temperature behavior is analyzed within the segmented rod
model of Fogler, Teber and Shklowskii, as originally developed for a
charge-ordered quasi one-dimensional electron crystal. The results are compared
with data obtained on as-grown and electron irradiated epitaxial TTF-TCNQ thin
films of the two-domain type
Ultra-fast vortex motion in dirty Nb-C superconductor with a close-to-perfect edge barrier
The ultra-fast dynamics of superconducting vortices harbors rich physics
generic to nonequilibrium collective systems. The phenomenon of flux-flow
instability (FFI), however, prevents its exploration and sets practical limits
for the use of vortices in various applications. To suppress the FFI, a
superconductor should exhibit a rarely achieved combination of properties: weak
volume pinning, close-to-depairing critical current, and fast heat removal from
heated electrons. Here, we demonstrate experimentally ultra-fast vortex motion
at velocities of 10-15 km/s in a directly written Nb-C superconductor in which
a close-to-perfect edge barrier orders the vortex motion at large current
values. The spatial evolution of the FFI is described using the edge-controlled
FFI model, implying a chain of FFI nucleation points along the sample edge and
their development into self-organized Josephson-like junctions (vortex rivers).
In addition, our results offer insights into the applicability of widely used
FFI models and suggest Nb-C to be a good candidate material for fast
single-photon detectors.Comment: 12 pages, 7 page
Cherenkov radiation of spin waves by ultra-fast moving magnetic flux quanta
Despite theoretical predictions for a Cherenkov-type radiation of spin waves
(magnons) by various propagating magnetic perturbations, fast-enough moving
magnetic field stimuli have not been available so far. Here, we experimentally
realize the Cherenkov radiation of spin waves in a Co-Fe magnonic conduit by
fast-moving (>1 km/s) magnetic flux quanta (Abrikosov vortices) in an adjacent
Nb-C superconducting strip. The radiation is evidenced by the microwave
detection of spin waves propagating a distance of 2 micrometers from the
superconductor and it is accompanied by a magnon Shapiro step in its
current-voltage curve. The spin-wave excitation is unidirectional and
monochromatic, with sub-40 nm wavelengths determined by the period of the
vortex lattice. The phase-locking of the vortex lattice with the excited spin
wave limits the vortex velocity and reduces the dissipation in the
superconductor.Comment: 11 pages, 5 page
Magnetotransport properties of iron microwires fabricated by focused electron beam induced autocatalytic growth
We have prepared iron microwires in a combination of focused electron beam
induced deposition (FEBID) and autocatalytic growth from the iron
pentacarbonyl, Fe(CO)5, precursor gas under UHV conditions. The electrical
transport properties of the microwires were investigated and it was found that
the temperature dependence of the longitudinal resistivity (rhoxx) shows a
typical metallic behaviour with a room temperature value of about 88
micro{\Omega} cm. In order to investigate the magnetotransport properties we
have measured the isothermal Hall-resistivities in the range between 4.2 K and
260 K. From these measurements positive values for the ordinary and the
anomalous Hall coefficients were derived. The relation between anomalous Hall
resistivity (rhoAN) and longitudinal resistivity is quadratic, rhoAN rho^2 xx,
revealing an intrinsic origin of the anomalous Hall effect. Finally, at low
temperature in the transversal geometry a negative magnetoresistance of about
0.2 % was measured
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