3,161 research outputs found
Three-dimensional magnetic flux-closure patterns in mesoscopic Fe islands
We have investigated three-dimensional magnetization structures in numerous
mesoscopic Fe/Mo(110) islands by means of x-ray magnetic circular dichroism
combined with photoemission electron microscopy (XMCD-PEEM). The particles are
epitaxial islands with an elongated hexagonal shape with length of up to 2.5
micrometer and thickness of up to 250 nm. The XMCD-PEEM studies reveal
asymmetric magnetization distributions at the surface of these particles.
Micromagnetic simulations are in excellent agreement with the observed magnetic
structures and provide information on the internal structure of the
magnetization which is not accessible in the experiment. It is shown that the
magnetization is influenced mostly by the particle size and thickness rather
than by the details of its shape. Hence, these hexagonal samples can be
regarded as model systems for the study of the magnetization in thick,
mesoscopic ferromagnets.Comment: 12 pages, 11 figure
Ultrafast dynamics of a magnetic antivortex - Micromagnetic simulations
The antivortex is a fundamental magnetization structure which is the
topological counterpart of the well-known magnetic vortex. We study here the
ultrafast dynamic behavior of an isolated antivortex in a patterned Permalloy
thin-film element. Using micromagnetic simulations we predict that the
antivortex response to an ultrashort external field pulse is characterized by
the production of a new antivortex as well as of a temporary vortex, followed
by an annihilation process. These processes are complementary to the recently
reported response of a vortex and, like for the vortex, lead to the reversal of
the orientation of the antivortex core region. In addition to its fundamental
interest, this dynamic magnetization process could be used for the generation
and propagation of spin waves for novel logical circuits.Comment: 4 pages, 4 figures. To be published in Physical Review B (R
The Thermal Conductance of Sapphire Ball Based Detector Clamps
In order to provide secure clamping with a low thermal conductance, some low
temperature detectors are held with point contact sapphire ball clamps. While
this method is increasingly common, the thermal conductance across this
interface has not been well studied. We present a direct measurement of the
thermal conductance of such clamps between 200 and 600~mK, with a clamping
force of approximately 2.7~~N/clamp. The thermal conductance of a
single sapphire-on-copper clamp was found to be
660~~[nW/K]. For a sapphire-on-silicon clamp the
conductance was found to be 380~~[nW/K]. The
conductance measured is consistent with thermal boundary resistance.Comment: 8 pages, 4 figures, Proceedings for the 19th International Workshop
on Low Temperature Detectors (LTD19). J Low Temp Phys (2022
Conductance of Distorted Carbon Nanotubes
We have calculated the effects of structural distortions of armchair carbon
nanotubes on their electrical transport properties. We found that the bending
of the nanotubes decreases their transmission function in certain energy ranges
and leads to an increased electrical resistance. Electronic structure
calculations show that these energy ranges contain localized states with
significant - hybridization resulting from the increased curvature
produced by bending. Our calculations of the contact resistance show that the
large contact resistances observed for SWNTs are likely due to the weak
coupling of the NT to the metal in side bonded NT-metal configurations.Comment: 5 pages RevTeX including 4 figures, submitted to PR
Transfer of Training Emotionally Biased Interpretations
Non-anxious college students first performed a semantic-judgement task that was designed to train either threat-related or threat-unrelated interpretations of threat-ambiguous homographs (e.g. mug). Next they performed an ostensibly separate transfer task of constructing personal mental images for single words, in a series that included new, threat-ambiguous homographs. In two experiments, the number of threat-related interpretations in the transfer task significantly increased following threat-related experience during the training phase, compared to other training conditions. We conclude that interpretive biases typically shown by anxious people can be established in non-anxious students in ways that generalize to novel tasks and materials
Luttinger liquid behavior in multi-wall carbon nanotubes
The low-energy theory for multi-wall carbon nanotubes including the
long-ranged Coulomb interactions, internal screening effects, and
single-electron hopping between graphite shells is derived and analyzed by
bosonization methods. Characteristic Luttinger liquid power laws are found for
the tunneling density of states, with exponents approaching their Fermi liquid
value only very slowly as the number of conducting shells increases. With minor
modifications, the same conclusions apply to transport in ropes of single-wall
nanotubes.Comment: 4 pages Revte
Predispositions and the Political Behavior of American Economic Elites: Evidence from Technology Entrepreneurs
Economic elites regularly seek to exert political influence. But what policies do they support? Many accounts implicitly assume economic elites are homogeneous and that increases in their political power will increase inequality. We shed new light on heterogeneity in economic elites' political preferences, arguing that economic elites from an industry can share distinctive preferences due in part to sharing distinctive predispositions. Consequently, how increases in economic elites' influence affect inequality depends on which industry's elites are gaining influence and which policy issues are at stake. We demonstrate our argument with four original surveys, including the two largest political surveys of American economic elites to date: one of technology entrepreneurs—whose influence is burgeoning—and another of campaign donors. We show that technology entrepreneurs support liberal redistributive, social, and globalistic policies but conservative regulatory policies—a bundle of preferences rare among other economic elites. These differences appear to arise partly from their distinctive predispositions
Tuning the domain wall orientation in thin magnetic strips by induced anisotropy
We report on a method to tune the orientation of in-plane magnetic domains
and domain walls in thin ferromagnetic strips by manipulating the magnetic
anisotropy. Uniaxial in-plane anisotropy is induced in a controlled way by
oblique evaporation of magnetic thin strips. A direct correlation between the
magnetization direction and the domain wall orientation is found experimentally
and confirmed by micromagnetic simulations. The domain walls in the strips are
always oriented along the oblique evaporation-induced easy axis, in spite of
the shape anisotropy. The controlled manipulation of domain wall orientations
could open new possibilities for novel devices based on domain-wall
propagation
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