422 research outputs found
Tuning magnetic chirality by dipolar interactions
Chiral magnetism has gained enormous interest in recent years because of the
anticipated wealth of applications in nanoelectronics. The demonstrated
stabilization of chiral magnetic domain walls and skyrmions has been attributed
to the actively investigated Dzyaloshinskii-Moriya interaction. Recently,
however, predictions were made that suggest dipolar interactions can also
stabilize chiral domain walls and skyrmions, but direct experimental evidence
has been lacking. Here we show that dipolar interactions can indeed stabilize
chiral domain walls by directly imaging the magnetic domain walls using
scanning electron microscopy with polarization analysis. We further show that
the competition between the Dzyaloshinskii-Moriya and dipolar interactions can
reverse the domain-wall chirality. Finally, we suggest that this competition
can be tailored by a Ruderman-Kittel-Kasuya-Yosida interaction. Our work
therefore reveals that dipolar interactions play a key role in the
stabilization of chiral spin textures. This insight will open up new routes
towards balancing interactions for the stabilization of chiral magnetism
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Micromagnetic investigation of domain and domain wall evolution through the spin-reorientation transition of an epitaxial NdCo5 film
The domain pattern and the domain wall microstructure throughout the spin-reorientation transition of an epitaxial NdCo5 thin film are investigated by micromagnetic simulations. The temperature-dependent anisotropy constants K1 and K2, which define the anisotropy energy term in the model, are chosen to reflect the easy axis—easy cone—easy plane spin-reorientation transition observed in epitaxial NdCo5 thin films. Starting at the high-temperature easy c-axis regime, the anisotropy constants are changed systematically corresponding to a lowering of the temperature of the system. The character of the domain walls and their profiles are analysed. The calculated domain configurations are compared to the experimentally observed temperature-dependent domain structure of an in-plane textured NdCo5 thin film
Homochiral antiferromagnetic merons, antimerons and bimerons realized in synthetic antiferromagnets
The ever-growing demand for device miniaturization and energy efficiency in
data storage and computing technology has prompted a shift towards
antiferromagnetic (AFM) topological spin textures as information carriers,
owing to their negligible stray fields, leading to possible high device density
and potentially ultrafast dynamics. We realize, in this work, such chiral
in-plane (IP) topological antiferromagnetic spin textures, namely merons,
antimerons, and bimerons in synthetic antiferromagnets by concurrently
engineering the effective perpendicular magnetic anisotropy, the interlayer
exchange coupling, and the magnetic compensation ratio. We demonstrate by
three-dimensional vector imaging of the N\'eel order parameter, the topology of
those spin textures and reveal globally a well-defined chirality, which is a
crucial requirement for controlled current-induced dynamics. Our analysis
reveals that the interplay between interlayer exchange and interlayer magnetic
dipolar interactions plays a key role in significantly reducing the critical
strength of the Dzyaloshinskii-Moriya interaction required to stabilize
topological spin textures, such as AFM merons, making synthetic
antiferromagnets a promising platform for next-generation spintronics
applications.Comment: 18pages, 5 figure
Influence of elastically pinned magnetic domain walls on magnetization reversal in multiferroic heterostructures
In elastically coupled multiferroic heterostructures that exhibit full domain correlations between ferroelectricand ferromagnetic subsystems, magnetic domain walls are firmly pinned on top of ferroelectric domainboundaries. In this work, we investigate the influence of pinned magnetic domain walls on the magnetizationreversal process in a Co40Fe40B20 wedge film that is coupled to a ferroelectric BaTiO3 substrate via interfacestrain transfer.We show that the magnetic field direction can be used to select between two distinct magnetizationreversal mechanisms, namely, (1) double switching events involving alternate stripe domains at a time or(2) synchronized switching of all domains. Furthermore, scaling of the switching fields with domain widthand film thickness is also found to depend on the field orientation. These results are explained by considering the dissimilar energies of the two types of pinned magnetic domain walls that are formed in the system.Peer reviewe
Enabling time-resolved 2D spatial-coherence measurements using the Fourier-analysis method with an integrated curved-grating beam monitor
Direct 2D spatial-coherence measurements are increasingly gaining importance at synchrotron beamlines, especially due to present and future upgrades of synchrotron facilities to diffraction-limited storage rings. We present a method to determine the 2D spatial coherence of synchrotron radiation in a direct and particularly simple way by using the Fourier-analysis method in conjunction with curved gratings. Direct photon-beam monitoring provided by a curved grating circumvents the otherwise necessary separate determination of the illuminating intensity distribution required for the Fourier-analysis method. Hence, combining these two methods allows for time-resolved spatial-coherence measurements. As a consequence, spatial-coherence degradation effects caused by beamline optics vibrations, which is one of the key issues of state-of-the-art X-ray imaging and scattering beamlines, can be identified and analyzed. © 2020 Optical Society of America
Direct 2D spatial coherence determination using the Fourier analysis method Multi parameter characterization of the P04 beamline at PETRA III
We present a systematic 2D spatial-coherence analysis of the soft-X-ray beamline P04 at PETRA III for various beamline configurations. The influence of two different beam-defining apertures on the spatial coherence properties of the beam is discussed and optimal conditions for coherence-based experiments are found. A significant degradation of the spatial coherence in the vertical direction has been measured and sources of this degradation are identified and discussed. The Fourier-analysis method, which gives fast and simple access to the 2D spatial coherence function of the X-ray beam, is used for the experiment. Here, we exploit the charge scattering of a disordered nanodot sample allowing the use of arbitrary X-ray photon energies with this method
Electrical parameters and water permeability properties of monolayers formed by T84 cells cultured on permeable supports
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