9,360 research outputs found
Pump-Probe Experiments on the Single-Molecule Magnet Fe8 : Measurement of Excited Level Lifetimes
We present magnetization measurements on the single molecule magnet Fe8 in
the presence of pulsed microwave radiation. A pump-probe technique is used with
two microwave pulses with frequencies of 107 GHz and 118 GHz and pulse lengths
of several nanoseconds to study the spin dynamics via time-resolved
magnetization measurements using a Hall probe magnetometer. We find evidence
for short spin-phonon relaxation times of the order of one microsecond. The
temperature dependence of the spin-phonon relaxation time in our experiments is
in good agreement with previously published theoretical results. We also
established the presence of very short energy diffusion times, that act on a
timescale of about 70 ns.Comment: submitted to Phys. Rev. Lett. (01 March 2007
The clustering and bias of radio-selected AGN and star-forming galaxies in the COSMOS field
Dark matter haloes in which galaxies reside are likely to have a significant
impact on their evolution. We investigate the link between dark matter haloes
and their constituent galaxies by measuring the angular two-point correlation
function of radio sources, using recently released 3 GHz imaging over $\sim 2 \
\mathrm{deg}^2z<1b = 1.5
^{+0.1}_{-0.2}z=0.62b = 2.1\pm 0.2b =
2.9 \pm 0.3b = 1.8^{+0.4}_{-0.5}z \sim 0.7M_{h} \sim 3-4
\times 10^{13}h^{-1}_{\odot}M_{h} \sim 1-2 \times
10^{13}h^{-1}_{\odot}z \ge 1z<1$.Comment: 20 pages, 10 figures, 1 table, accepted by MNRA
Coherent control of magnetization precession in ferromagnetic semiconductor (Ga,Mn)As
We report single-color, time resolved magneto-optical measurements in
ferromagnetic semiconductor (Ga,Mn)As. We demonstrate coherent optical control
of the magnetization precession by applying two successive ultrashort laser
pulses. The magnetic field and temperature dependent experiments reveal the
collective Mn-moment nature of the oscillatory part of the time-dependent Kerr
rotation, as well as contributions to the magneto-optical signal that are not
connected with the magnetization dynamics.Comment: 6 pages, 3 figures, accepted in Applied Physics Letter
Acute lower limb ischemia due to thrombo-embolic arterial occlusions in two previously healthy men with markedly elevated Lp(a)
Lipoprotein (a) (Lp(a)) is a well-documented risk factor for atherosclerotic cardiovascular disease. Its role in acute thrombo-embolic occlusions of peripheral arteries is not known. We describe two cases of multiple, acute, peripheral arterial occlusions in two previously healthy men with markedly elevated Lp(a). Both cases had unsatisfactory results after percutaneous and surgical revascularization procedures. Experience yielded in these two cases suggests that when an unfavorable outcome occurs in a peripheral artery disease patient in the absence of the regular risk factors, Lp(a) should be determined and its role investigated
From laterally modulated two-dimensional electron gas towards artificial graphene
Cyclotron resonance has been measured in far-infrared transmission of
GaAs/AlGaAs heterostructures with an etched hexagonal lateral
superlattice. Non-linear dependence of the resonance position on magnetic field
was observed as well as its splitting into several modes. Our explanation,
based on a perturbative calculation, describes the observed phenomena as a weak
effect of the lateral potential on the two-dimensional electron gas. Using this
approach, we found a correlation between parameters of the lateral patterning
and the created effective potential and obtain thus insights on how the
electronic miniband structure has been tuned. The miniband dispersion was
calculated using a simplified model and allowed us to formulate four basic
criteria that have to be satisfied to reach graphene-like physics in such
systems
Influence of antisymmetric exchange interaction on quantum tunneling of magnetization in a dimeric molecular magnet Mn6
We present magnetization measurements on the single molecule magnet Mn6,
revealing various tunnel transitions inconsistent with a giant-spin
description. We propose a dimeric model of the molecule with two coupled spins
S=6, which involves crystal-field anisotropy, symmetric Heisenberg exchange
interaction, and antisymmetric Dzyaloshinskii-Moriya exchange interaction. We
show that this simplified model of the molecule explains the experimentally
observed tunnel transitions and that the antisymmetric exchange interaction
between the spins gives rise to tunneling processes between spin states
belonging to different spin multiplets.Comment: 5 pages, 4 figure
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