113 research outputs found
Domain walls in (Ga,Mn)As diluted magnetic semiconductor
We report experimental and theoretical studies of magnetic domain walls in an
in-plane magnetized (Ga,Mn)As dilute moment ferromagnetic semiconductor. Our
high-resolution electron holography technique provides direct images of domain
wall magnetization profiles. The experiments are interpreted based on
microscopic calculations of the micromagnetic parameters and
Landau-Lifshitz-Gilbert simulations. We find that the competition of uniaxial
and biaxial magnetocrystalline anisotropies in the film is directly reflected
in orientation dependent wall widths, ranging from approximately 40 nm to 120
nm. The domain walls are of the N\'eel type and evolve from near-
walls at low-temperatures to large angle [10]-oriented walls and small
angle [110]-oriented walls at higher temperatures.Comment: 5 pages, 4 figure
On the interpretation of spin-polarized electron energy loss spectra
We study the origin of the structure in the spin-polarized electron energy
loss spectroscopy (SPEELS) spectra of ferromagnetic crystals. Our study is
based on a 3d tight-binding Fe model, with constant onsite Coulomb repulsion U
between electrons of opposite spin. We find it is not the total density of
Stoner states as a function of energy loss which determines the response of the
system in the Stoner region, as usually thought, but the densities of Stoner
states for only a few interband transitions. Which transitions are important
depends ultimately on how strongly umklapp processes couple the corresponding
bands. This allows us to show, in particular, that the Stoner peak in SPEELS
spectra does not necessarily indicate the value of the exchange splitting
energy. Thus, the common assumption that this peak allows us to estimate the
magnetic moment through its correlation with exchange splitting should be
reconsidered, both in bulk and surface studies. Furthermore, we are able to
show that the above mechanism is one of the main causes for the typical
broadness of experimental spectra. Finally, our model predicts that optical
spin waves should be excited in SPEELS experiments.Comment: 11 pages, 7 eps figures, REVTeX fil
Proposal for a standard problem for micromagnetic simulations including spin-transfer torque
The spin-transfer torque between itinerant electrons and the magnetization in a ferromagnet is of fundamental interest for the applied physics community. To investigate the spin-transfer torque, powerful simulation tools are mandatory. We propose a micromagnetic standard problem includingthe spin-transfer torque that can be used for the validation and falsication of micromagnetic simulation tools. The work is based on the micromagnetic model extended by the spin-transfer torque in continuously varying magnetizations as proposed by Zhang and Li. The standard problem geometry is a permalloy cuboid of 100 nm edge length and 10 nm thickness, which contains a Landau pattern with a vortex in the center of the structure. A spin-polarized dc current density of 1012 A/m2 flows laterally through the cuboid and moves the vortex core to a new steady-state position. We show that the new vortex-core position is a sensitive measure for the correctness of micromagnetic simulatorsthat include the spin-transfer torque. The suitability of the proposed problem as a standard problem is tested by numerical results from four different finite-difference and finite-element-based simulation tools
HICS: Highly charged ion collisions with surfaces
The layout of a new instrument designed to study the interaction of highly
charged ions with surfaces, which consists of an ion source, a beamline
including charge separation and a target chamber, is presented here. By varying
the charge state and impact velocity of the projectiles separately, the
dissipation of potential and kinetic energy at or below the surface can be
studied independently. The target chamber offers the use of tunable
metal-insulator-metal devices as detectors for internal electronic excitation,
a timeof-flight system to study the impact induced particle emission and the
possibility to transfer samples in situ to a UHV scanning probe microscope.
Samples and detectors can be prepared in situ as well. As a first example data
on graphene layers on SrTiO3 which have been irradiated with Xe36+ are
presented.
Key words: highly charged ions, sputtering, AFM, grapheneComment: 4 pages, 4 figures, conference proceeding to 17th Internat. Workshop
for Ion Surf. Collision
Adsorption of CO on a Platinum (111) surface - a study within a four-component relativistic density functional approach
We report on results of a theoretical study of the adsorption process of a
single carbon oxide molecule on a Platinum (111) surface. A four-component
relativistic density functional method was applied to account for a proper
description of the strong relativistic effects. A limited number of atoms in
the framework of a cluster approach is used to describe the surface. Different
adsorption sites are investigated. We found that CO is preferably adsorbed at
the top position.Comment: 23 Pages with 4 figure
A Systematic Review of Music Therapy Practice and Outcomes with Acute Adult Psychiatric In-Patients
PMCID: PMC3732280This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Immunohistochemical analysis of p53 in vulval intraepithelial neoplasia and vulval squamous cell carcinoma
Familiarity bias and physiological responses in contagious yawning by dogs support link to empathy
In humans, the susceptibility to yawn contagion has been theoretically and empirically related to our capacity for empathy. Because of its relevance to evolutionary biology, this phenomenon has been the focus of recent investigations in nonhuman species. In line with the empathic hypothesis, contagious yawning has been shown to correlate with the level of social attachment in several primate species. Domestic dogs (Canis familiaris) have also shown the ability to yawn contagiously. To date, however, the social modulation of dog contagious yawning has received contradictory support and alternative explanations (i.e., yawn as a mild distress response) could explain positive evidence. The present study aims to replicate contagious yawning in dogs and to discriminate between the two possible mediating mechanisms (i.e., empathic vs. distress related response). Twenty-five dogs observed familiar (dog’s owner) and unfamiliar human models (experimenter) acting out a yawn or control mouth movements. Concurrent physiological measures (heart rate) were additionally monitored for twenty-one of the subjects. The occurrence of yawn contagion was significantly higher during the yawning condition than during the control mouth movements. Furthermore, the dogs yawned more frequently when watching the familiar model than the unfamiliar one demonstrating that the contagiousness of yawning in dogs correlated with the level of emotional proximity. Moreover, subjects’ heart rate did not differ among conditions suggesting that the phenomenon of contagious yawning in dogs is unrelated to stressful events. Our findings are consistent with the view that contagious yawning is modulated by affective components of the behavior and may indicate that rudimentary forms of empathy could be present in domesticated dogs
Striking coincidences: How realists should reason about them
Many metaethicists assume that our normative judgments are both by and large true, and the product of causal forces. In other words, many metaethicists assume that the set of normative judgments that causal forces have led us to make largely coincides with the set of true normative judgments. How should we explain this coincidence? This is what Sharon Street (2006) calls the practical/theoretical puzzle. Some metaethicists can easily solve this puzzle, but not all of them can, Street argues; she takes the puzzle to constitute a specific challenge for normative realism. In this article I elucidate Street’s puzzle and outline possible solutions to it, framed in terms of a general strategy for reasoning about coincidences. I argue that the success of Street’s challenge crucially depends on how we set the ‘reference class’ of normative judgments that we could have endorsed, assuming realism. I conclude that while the practical/theoretical puzzle falls short of posing a general challenge for normative realism, it can be successful as a selective challenge for specific realist views
Establishment of a model for equine small intestinal disease: effects of extracorporeal blood perfusion of equine ileum on metabolic variables and histological morphology – an experimental ex vivo study
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