679 research outputs found
AMORPHOUS PD-SI ALLOYS AND HYDRIDES PREPARED BY LOW-TEMPERATURE ION-IMPLANTATION
Ion implantation simultaneously produces compositional changes and radiation damage in the target. If the latter is not annealed, amorphization should ultimately result. Can implantation of a covalent solute into a transition metal host stabilize the damage and hence produce an amorphous alloy at lower concentrations than other techniques ? We have studied the composition-dependence of the resistivity and TCR of thin (600-800 Å) Pd films implanted at 6 K with Si ions : The results are compared to those obtained on the corresponding well-documented quench-condensed alloys, which are amorphous at Si concentrations ~.18. The resistivity of the implanted films saturates at about 90 µΩ·cm for Si concentrations above ~.18. Thus, the critical concentration for amorphization is presumably the same for the low-temperature implanted or quench-condensed Pd-Si alloy, confirming that local structure effects dominate amorphous alloy formation criteria. In a further experiment, hydrogen was implanted into the amorphous Pd-Si films (again at 6K). The resistivity increased sharply, doubling at H concentrations around 100 %. The resulting systems were superconducting ; their maximum critical temperature was 2.6 K
Inhomogeneous magnesium hydride synthesized by low temperature ion implantation: weak localization effect
Metastable MgHx hydride was prepared by H ion implantation into Mg films at 5 K. The resistivity and magnetoresistance temperature dependence reveal weak localization effects due to atomic disorder. At low hydrogen concentrations, x ≤0.3, the conductivity varies as σ∼log (T), typical of two-dimensional weak localization behaviour. The resistivity is also very sensitive to the sample inhomogeneity, due to H diffusion, which can be modelled by introducing a temperature-dependent geometrical percolating factor G. At higher H concentrations, 0.7 ≤x ≤3, after annealing at 20 K, 50 K and 110 K, the samples also exhibit weak localization but with three-dimensional behaviour i.e. a . Our analysis is consistent with the existence of an inhomogeneous system formed by a mixture of two phases with contrasted conduction properties, one of which is a well-behaved metal, while the other displays the localization properties. The results lead us to identify the former phase to a non percolating superconducting phase at low temperature
Probing the interface magnetism in the FeMn/NiFe exchange bias system using magnetic second harmonic generation
Second harmonic generation magneto-optic Kerr effect (SHMOKE) experiments,
sensitive to buried interfaces, were performed on a polycrystalline NiFe/FeMn
bilayer in which areas with different exchange bias fields were prepared using
5 KeV He ion irradiation. Both reversible and irreversible uncompensated spins
are found in the antiferromagnetic layer close to the interface with the
ferromagnetic layer. The SHMOKE hysteresis loop shows the same exchange bias
field as obtained from standard magnetometry. We demonstrate that the exchange
bias effect is controlled by pinned uncompensated spins in the
antiferromagnetic layer.Comment: submitted to Phys. Rev. Let
Ordering intermetallic alloys by ion irradiation: a way to tailor magnetic media
Combining He ion irradiation and thermal mobility below 600K, we both trigger
and control the transformation from chemical disorder to order in thin films of
an intermetallic ferromagnet (FePd). Kinetic Monte Carlo simulations show how
the initial directional short range order determines order propagation.
Magnetic ordering perpendicular to the film plane was achieved, promoting the
initially weak magnetic anisotropy to the highest values known for FePd films.
This post-growth treatment should find applications in ultrahigh density
magnetic recording.Comment: 7 pages, 3 Figure
Magnetic reversal in ion-irradiated FePt thin films
International audiencePrevious work on ion irradiation control of FePt thin films magnetic anisotropy is extended to ultrathin films (2-10nm). The effects of 30keV He ion irradiation on the magnetic properties are explored as a function of ion fluence and film thickness. Depending on their growth conditions, the thinnest films exhibit different magnetic properties. Although this affects their final magnetic behaviour, we show that after irradiation at 300 @BULLET C the easy magnetization axis may rotate entirely from inplane to out-of-plane at very low fluences, e.g. 2×10 13 He + /cm 2 on 5 nm thick film. This demonstrates the extreme sensitivity of the magnetic anisotropy to ion-induced local L1 0 ordering. Under these conditions, ultrathin films may exhibit perfectly square hysteresis loops with 100% remnant magnetization and low coercivity
Isotopic and velocity distributions of Bi produced in charge-pickup reactions of 208Pb at 1 A GeV
Isotopically resolved cross sections and velocity distributions have been
measured in charge-pickup reactions of 1 A GeV 208Pb with proton, deuterium and
titanium target. The total and partial charge-pickup cross sections in the
reactions 208Pb + 1H and 208Pb + 2H are measured to be the same in the limits
of the error bars. A weak increase in the total charge-pickup cross section is
seen in the reaction of 208Pb with the titanium target. The measured velocity
distributions show different contributions - quasi-elastic scattering and
Delta-resonance excitation - to the charge-pickup production. Data on total and
partial charge-pickup cross sections from these three reactions are compared
with other existing data and also with model calculations based on the coupling
of different intra-nuclear cascade codes and an evaporation code.Comment: 20 pages, 12 figures, background information on
http://www-w2k.gsi.de/kschmidt
Production of neutron-rich nuclei in fragmentation reactions of 132Sn projectiles at relativistic energies
The fragmentation of neutron-rich 132Sn nuclei produced in the fission of
238U projectiles at 950 MeV/u has been investigated at the FRagment Separator
(FRS) at GSI. This work represents the first investigation of fragmentation of
medium-mass radioactive projectiles with a large neutron excess. The measured
production cross sections of the residual nuclei are relevant for the possible
use of a two-stage reaction scheme (fission+fragmentation) for the production
of extremely neutron-rich medium-mass nuclei in future rare-ion-beam
facilities. Moreover, the new data will provide a better understanding of the
"memory" effect in fragmentation reactions.Comment: 5 pages, 3 figure
Experimental Indications for the Response of the Spectators to the Participant Blast
Precise momentum distributions of identified projectile fragments, formed in
the reactions 238U + Pb and 238U + Ti at 1 A GeV, are measured with a
high-resolution magnetic spectrometer. With increasing mass loss, the
velocities first decrease as expected from previously established systematics,
then level off, and finally increase again. Light fragments are on the average
even faster than the projectiles. This finding is interpreted as the response
of the spectators to the participant blast. The re-acceleration of projectile
spectators is sensitive to the nuclear mean field and provides a new tool for
investigating the equation of state of nuclear matter.Comment: 7 pages, 3 figures, background information on
http://www-wnt.gsi.de/kschmidt
Genetic differentiation of brackish water populations of cod Gadus morhua in the southern Baltic, inferred from genotyping using SNP-arrays
The Baltic is a semi-enclosed sea characterised by decreasing salinity in the eastern and northern direction with only the deeper parts of the southern Baltic suitable as spawning grounds for marine species like cod. Baltic cod exhibits various adaptations to brackish water conditions, yet the inflow of salty North Sea water near the bottom remains an influence on the spawning success of the Baltic cod. The eastern Baltic population has been very weakly studied in comparison with the western population.
The aim of this study is to demonstrate for the first time genetic differentiation by the use of a large number of SNPs between eastern and western Baltic populations existing in differentiated salinity conditions. Two cod samples were collected from the Bay of Gdańsk, Poland and one from the Kiel Bight, Germany. Samples were genotyped using a cod derived SNP-array (Illumina) with 10 913 SNPs. A selection of diagnostic SNPs was performed. A set of 7944 validated SNPs were analysed to assess the differentiation of three samples of cod. Results indicated a clear distinctness of the Kiel Bight from the populations of the eastern Baltic. FST comparison between both eastern samples was non-significant. Clustering analysis, principal coordinates analysis and assignment test clearly indicated that the eastern samples should be considered as one subpopulation, well differentiated from the western subpopulation. With the SNP approach, no differentiation between groups containing ‘healthy’ and ‘non-healthy’ cod individuals was observed
Identification and Decomposition of Five Dominant Wild Plants From Acid Swampland in South Sumatra
There were five emergence plants in swampland such as Polygonum barbatum, Neptunia prostrata, Phragmites karka, Ludwigia adscendens and Phragmites communis, which might be used for compost source, all the plants were easily adapted and grew very well on acid soil. These plants were choosen because of abudancy and size. All plants were identified, collected, chopped and weighted then put in a 50 liters plastic drum for decomposting during 12 weeks. Composts temperature were monitored every week, nutrients content (N, P, K, Ca, Mg, Na) and compost chemical properties (C-organic, C.E.C., C/N ratio) were analysed every two weeks. Results showed that each compost from different plant varied in nutrients content and chemical properties. Compost made of Neptunia prostata Lam. contained highest nutrients than others, it’s nutrients were N (4%), P (1675 mg kg-1), K (5.6 %), Ca (0.32 %), Mg (0.32 %) and Na (0.12 %) and the lowest nutrients content showed by compost of Phragmites karka Retz. in which N (2.4 %), P (1160 mg kg-1), K (2.62 %), Ca (0.04 %), Mg (0.07 %), and Na (0.03 %). It seem broadleaf plants tended to have higher nutrients content than grasses or graminae. Neptunia prostrata compost had a high N content due to it’s leguminosae plant. Al and Fe were low in all composts, therefore all plants were recommended for organic nutrient sources. [How to Cite: Siti MB, A Wijaya, EP Sagala and SNA Fitri. 2015. Identification and Decomposition of Five Dominant Wild plants from Acid Swampland in South Sumatra. J Trop Soils 20: 149-155. Doi: 10.5400/jts.2015.20.3.149][Permalink/DOI: www.dx.doi.org/10.5400/jts.2015.20.3.149] 
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