Search results for "DOMAIN"
showing 10 items of 2485 documents
Concept Maps for Comprehension and Navigation of Hypertexts
2013
Comprehension and learning with hypertexts are challenging due to the nonlinearity of such digital documents. Processing hypertexts may involve navigation and comprehension problems, leading learners to cognitive overhead. Concept maps have been added to hypertexts to reduce the cognitive requirements of navigation and comprehension. This chapter explores the literature to examine the effects of concept maps on navigation, comprehension, and learning from hypertexts. The literature review aims to elucidate how concept maps may contribute to processing hypertexts and under which conditions. In spite of the variability of concept maps used in hypertexts, some findings converge. Concept maps r…
Effect of boundary-induced chirality on magnetic textures in thin films
2018
In the quest for miniaturizing magnetic devices, the effects of boundaries and surfaces become increasingly important. Here we show how the recently predicted boundary-induced Dzyaloshinskii-Moriya interaction (DMI) affects the magnetization of ferromagnetic films with a $C_{\infty v}$ symmetry and a perpendicular magnetic anisotropy. For an otherwise uniformly magnetized film, we find a surface twist when the magnetization in the bulk is canted by an in-plane external field. This twist at the surfaces caused by the boundary-induced DMI differs from the common canting caused by internal DMI observed at the edges of a chiral magnet. Further, we find that the surface twist due to the boundary…
Imaging of current induced Néel vector switching in antiferromagnetic Mn 2 Au
2019
The effects of current induced N\'eel spin-orbit torques on the antiferromagnetic domain structure of epitaxial Mn$_2$Au thin films were investigated by X-ray magnetic linear dichroism - photoemission electron microscopy (XMLD-PEEM). We observed current induced switching of AFM domains essentially corresponding to morphological features of the samples. Reversible as well as irreversible N\'eel vector reorientation was obtained in different parts of the samples and the switching of up to 30 % of all domains in the field of view of 10 $\mu$m is demonstrated. Our direct microscopical observations are compared to and fully consistent with anisotropic magnetoresistance effects previously attribu…
Mechanism of Néel Order Switching in Antiferromagnetic Thin Films Revealed by Magnetotransport and Direct Imaging.
2019
We probe the current-induced magnetic switching of insulating antiferromagnet/heavy metals systems, by electrical spin Hall magnetoresistance measurements and direct imaging, identifying a reversal occurring by domain wall (DW) motion. We observe switching of more than one third of the antiferromagnetic domains by the application of current pulses. Our data reveal two different magnetic switching mechanisms leading together to an efficient switching, namely the spin-current induced effective magnetic anisotropy variation and the action of the spin torque on the DWs.
Time-resolved imaging of pulse-induced magnetization reversal with a microwave assist field
2015
AbstractThe reversal of the magnetization under the influence of a field pulse has been previously predicted to be an incoherent process with several competing phenomena such as domain wall relaxation, spin wave-mediated instability regions and vortex-core mediated reversal dynamics. However, there has been no study on the direct observation of the switching process with the aid of a microwave signal input. We report a time-resolved imaging study of magnetization reversal in patterned magnetic structures under the influence of a field pulse with microwave assistance. The microwave frequency is varied to demonstrate the effect of resonant microwave-assisted switching. We observe that the swi…
Multiferroic BiFeO<inf>3</inf> for conductance control at the LaAlO<inf>3</inf>/SrTiO<inf>3</inf>-interface
2015
Multiferroic materials possessing both magnetic and ferroelectric order enable in principle to switch order parameters using not the direct reciprocal field, e.g. to switch the magnetization by an electric field or the electric polarization by a magnetic field. A recent breakthrough was achieved by the demonstration of the ferromagnetic switching of a Co layer with an electric field employing the multiferroic BiFeO 3 [1]. The latter material is a perovskite based oxide that shows stable ferro-electricity as well as an antiferromagnetic order at room temperature [2,3]. Due to a Dzyaloshinskii-Moriya interaction induced by rotation of oxygen octahedra leading to noncollinear Fe-O-Fe bonds a s…
Temperature-induced martensite in magnetic shape memory Fe2MnGa observed by photoemission electron microscopy
2012
The magnetic domain structure in single crystals of a Heusler shape memory compound near the composition Fe2MnGa was observed during phase transition by photoelectron emission microscopy at Beamline 11.0.1.1 of the Advanced Light Source. The behavior is comparable with recent observations of an adaptive martensite phase in prototype Ni2MnGa, although the pinning in the recent work is an epitaxial interface and in this work the effective pinning plane is a boundary between martensitic variants that transform in a self-accommodating way from the single crystal austenite phase present at high temperatures. Temperature dependent observations of the twinning structure give information as to the …
Spin-transfer torque driven motion, deformation, and instabilities of magnetic skyrmions at high currents
2020
In chiral magnets, localized topological magnetic whirls, magnetic skyrmions, can be moved by spin polarized electric currents. Upon increasing the current strength, with prospects for high-speed skyrmion motion for spintronics applications in mind, isolated skyrmions deform away from their typical circular shape. We analyze the influence of spin-transfer torques on the shape of a single skyrmion, including its stability upon adiabatically increasing the strength of the applied electric current. For rather compact skyrmions at uniaxial anisotropies well above the critical anisotropy for domain wall formation, we find for high current densities that the skyrmion assumes a non-circular shape …
New expressions for string loop amplitudes leading to an ultrasimple conception of string dynamics
1991
New expressions are derived for string loop amplitudes as overlap integrals of string wave functionals. They are shown to take the form of exchange terms coming from the Bose-Einstein symmetrization between string segments. One is thus led to the ultrasimple conception that string theory is basically free, and that ``string interactions'' are merely due to the fact that strings are composite objects with Bose-Einstein segments as constituents.
Solitons and their observable signatures in quasi-one-dimensional systems
2005
We give an overview of the experimental signatures of nonlinear waves: notably topological and non topological solitons, in specific quasi-one-dimensional devices and condensed matter systems. Non topological solitons can be easily observed and manipulated, on a macroscopic scale, in optical fibers and electrical transmission lines. Topological solitons have been clearly identified as fluxons in Josephson transmission lines and as domain walls in condensed matter systems such as magnetic chains and synthetic polymers. By contrast, at the present time the observable signatures of nonlinear excitations such as pulse or envelope solitons and polarons, which are predicted to occur on a microsco…