195 research outputs found
Synthesis and Immobilization of Pt Nanoparticles on Amino-Functionalized Halloysite Nanotubes toward Highly Active Catalysts
A simple and effective method for the preparation of platinum nanoparticles (Pt NPs) grown on amino-functionalized halloysite nanotubes (HNTs) was developed. The nanostructures were synthesized through the functionalization of the HNTs, followed by an in situ approach to generate Pt NPs with diameter of approximately 1.5 nm within the entire HNTs. The synthesis process, composition and morphology of the nanostructures were characterized. The results suggest PtNPs/NH2-HNTs nanostructures with ultrafine PtNPs were successfully synthesized by green chemically-reducing H2PtCl6 without the use of surfactant. The nanostructures exhibit promising catalytic properties for reducing potassium hexacyanoferrate(III) to potassium hexacyanoferrate(II). The presented experiment for novel PtNPs/NH2-HNTs nanostructures is quite simple and environmentally benign, permitting it as a potential application in the future field of catalysts
Skyrmion-Bubble Bundles in an X-type Sr2Co2Fe28O46 Hexaferrite above Room Temperature
Magnetic skyrmions are spin swirls that possess topological nontriviality and
are considered particle-like entities. They are distinguished by an integer
topological charge Q. The presence of skyrmion bundles provides an opportunity
to explore the range of values for Q, which is crucial for the advancement of
topological spintronic devices with multi-Q properties. In this study, we
present a new material candidate, Sr2Co2Fe28O46 hexaferrite of the X-type,
which hosts small dipolar skyrmions at room temperature and above. By
exploiting reversed magnetic fields from metastable skyrmion bubbles at zero
fields, we can incorporate skyrmion-bubble bundles with different interior
skyrmion/bubble numbers, topological charges, and morphologies at room
temperature. Our experimental findings are consistently supported by
micromagnetic simulations. Our results highlight the versatility of topological
spin textures in centrosymmetric uniaxial magnets, thereby paving the way for
the development of room-temperature topological spintronic devices with multi-Q
characteristics.Comment: https://doi.org/10.1002/adma.20230611
Edge-Mediated Skyrmion Chain and Its Collective Dynamics in a Confined Geometry
The emergence of a topologically nontrivial vortex-like magnetic structure,
the magnetic skyrmion, has launched new concepts for memory devices. There,
extensive studies have theoretically demonstrated the ability to encode
information bits by using a chain of skyrmions in one-dimensional nanostripes.
Here, we report the first experimental observation of the skyrmion chain in
FeGe nanostripes by using high resolution Lorentz transmission electron
microscopy. Under an applied field normal to the nanostripes plane, we observe
that the helical ground states with distorted edge spins would evolves into
individual skyrmions, which assemble in the form of chain at low field and move
collectively into the center of nanostripes at elevated field. Such skyrmion
chain survives even as the width of nanostripe is much larger than the single
skyrmion size. These discovery demonstrates new way of skyrmion formation
through the edge effect, and might, in the long term, shed light on the
applications.Comment: 7 pages, 3 figure
Direct imaging of a zero-field target skyrmion and its polarity switch in a chiral magnetic nanodisk
A target skyrmion is a flux-closed spin texture that has two-fold degeneracy
and is promising as a binary state in next generation universal memories.
Although its formation in nanopatterned chiral magnets has been predicted, its
observation has remained challenging. Here, we use off-axis electron holography
to record images of target skyrmions in a 160-nm-diameter nanodisk of the
chiral magnet FeGe. We compare experimental measurements with numerical
simulations, demonstrate switching between two stable degenerate target
skyrmion ground states that have opposite polarities and rotation senses and
discuss the observed switching mechanism.Comment: 18 pages, 4 figure
Electrical Probing of Field-Driven Cascading Quantized Transitions of Skyrmion Cluster States in MnSi Nanowires
Magnetic skyrmions are topologically stable whirlpool-like spin textures that
offer great promise as information carriers for future ultra-dense memory and
logic devices1-4. To enable such applications, particular attention has been
focused on the skyrmions properties in highly confined geometry such as one
dimensional nanowires5-8. Hitherto it is still experimentally unclear what
happens when the width of the nanowire is comparable to that of a single
skyrmion. Here we report the experimental demonstration of such scheme, where
magnetic field-driven skyrmion cluster (SC) states with small numbers of
skyrmions were demonstrated to exist on the cross-sections of ultra-narrow
single-crystal MnSi nanowires (NWs) with diameters, comparable to the skyrmion
lattice constant (18 nm). In contrast to the skyrmion lattice in bulk MnSi
samples, the skyrmion clusters lead to anomalous magnetoresistance (MR)
behavior measured under magnetic field parallel to the NW long axis, where
quantized jumps in MR are observed and directly associated with the change of
the skyrmion number in the cluster, which is supported by Monte Carlo
simulations. These jumps show the key difference between the clustering and
crystalline states of skyrmions, and lay a solid foundation to realize
skyrmion-based memory devices that the number of skyrmions can be counted via
conventional electrical measurements
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