97 research outputs found
Magnetocrystalline anisotropy of Fe and Co slabs and clusters on SrTiO by first-principles
In this work, we present a detailed theoretical investigation of the
electronic and magnetic properties of ferromagnetic slabs and clusters
deposited on SrTiO via first-principles, with a particular emphasis on the
magneto-crystalline anisotropy (MCA). We found that in the case of Fe films
deposited on SrTiO the effect of the interface is to quench the MCA
whereas for Cobalt we observe a change of sign of the MCA from in-plane to
out-of-plane as compared to the free surface. We also find a strong enhancement
of MCA for small clusters upon deposition on a SrTiO substrate. The
hybridization between the substrate and the -orbitals of the cluster
extending in-plane for Fe and out-of-plane for Co is at the origin of this
enhancement of MCA. As a consequence, we predict that the Fe nanocrystals (even
rather small) should be magnetically stable and are thus good potential
candidates for magnetic storage devices.Comment: Physical ReviewB, 201
Out- versus in-plane magnetic anisotropy of free Fe and Co nanocrystals: tight-binding and first-principles studies
We report tight-binding (TB) and Density Function Theory (DFT) calculations
of magnetocrystalline anisotropy energy (MAE) of free Fe (body centerd cubic)
and Co (face centered cubic) slabs and nanocrystals. The nanocrystals are
truncated square pyramids which can be obtained experimentally by deposition of
metal on a SrTiO(001) substrate. For both elements our local analysis shows
that the total MAE of the nanocrystals is largely dominated by the contribution
of (001) facets. However, while the easy axis of Fe(001) is out-of-plane, it is
in-plane for Co(001). This has direct consequences on the magnetic reversal
mechanism of the nanocrystals. Indeed, the very high uniaxial anisotropy of Fe
nanocrystals makes them a much better potential candidate for magnetic storage
devices.Comment: 8 pages, 7 figure
Magnetocrystalline anisotropy energy of Fe, Fe slabs and nanoclusters: a detailed local analysis within a tight-binding model
We report tight-binding (TB) calculations of magnetocrystalline anisotropy
energy (MAE) of Iron slabs and nanoclusters with a particuler focus on local
analysis. After clarifying various concepts and formulations for the
determination of MAE, we apply our realistic TB model to the analysis of the
magnetic anisotropy of Fe, Fe slabs and of two large Fe clusters
with and facets only: a truncated pyramid and a truncated
bipyramid containg 620 and 1096 atoms, respectively. It is shown that the MAE
of slabs originates mainly from outer layers, a small contribution from the
bulk gives rise, however, to an oscillatory behavior for large thicknesses.
Interestingly, the MAE of the nanoclusters considered is almost solely due to
facets and the base perimeter of the pyramid. We believe that this fact
could be used to efficiently control the anisotropy of Iron nanoparticles and
could also have consequences on their spin dynamics
Magnetocrystalline anisotropy of Fe and Co slabs and clusters on SrTiO<sub>3</sub> by first-principles
Proposal for all-electrical skyrmion detection in van der Waals tunnel junctions
Based on rigorous first-principles calculations, we show that all-electrical
detection of skyrmions in 2D van der Waals (vdW) magnets is feasible in tunnel
junctions with straightforward implementation into device architectures. We use
the nonequilibrium Green's function method for quantum transport, including
self-energy due to electrodes and working conditions, going beyond the standard
Tersoff-Hamann approximation. An extremely large noncollinear magnetoresistance
(NCMR) of above 10,000 \% at the Fermi energy is predicted for a vdW tunnel
junction based on graphite/FeGeTe/germanene/graphite. We trace the
origin of the NCMR to spin-mixing between states of and
character at the surface atoms and the orbital matching effect at the
interface.Comment: 5 figure
A Sociolinguistic Study of Koreans in China: The ‘Language Socialization’ of Koreans in China
UniFolding: Towards Sample-efficient, Scalable, and Generalizable Robotic Garment Folding
This paper explores the development of UniFolding, a sample-efficient,
scalable, and generalizable robotic system for unfolding and folding various
garments. UniFolding employs the proposed UFONet neural network to integrate
unfolding and folding decisions into a single policy model that is adaptable to
different garment types and states. The design of UniFolding is based on a
garment's partial point cloud, which aids in generalization and reduces
sensitivity to variations in texture and shape. The training pipeline
prioritizes low-cost, sample-efficient data collection. Training data is
collected via a human-centric process with offline and online stages. The
offline stage involves human unfolding and folding actions via Virtual Reality,
while the online stage utilizes human-in-the-loop learning to fine-tune the
model in a real-world setting. The system is tested on two garment types:
long-sleeve and short-sleeve shirts. Performance is evaluated on 20 shirts with
significant variations in textures, shapes, and materials. More experiments and
videos can be found in the supplementary materials and on the website:
https://unifolding.robotflow.aiComment: CoRL 202
EVALUATION OF THE EFFECT OF EXTERNAL PRESTRESSED STEEL STRANDS ON CABLE-STAYED BRIDGES BASED ON FINITE ELEMENT ANALYSIS AND STATIC TEST
This article relies on the reinforcement project of the Mulinghe cable-stayed bridge to explore the changes in the mechanical properties of the reinforced concrete cable-stayed bridge before and after reinforcement. The bridge has large cable spacing, large internal force of a single cable, and the main beam is mainly Reinforced Concrete. Therefore, structural calculation, disease analysis, and damage state simulation are carried out. Afterwards, the bridge's commonly used reinforcement methods were compared, and suitable reinforcement schemes were selected. After the reinforcement, the field test was carried out on the cable-stayed bridge, the main beam deflection, the strain of the main beam and the main tower, and the increase in the cable force of the cable- stayed were analyzed. The results show that external prestressed reinforcement is the best way, which can significantly reduce the vertical displacement of the main beam and the horizontal displacement of the main tower, and also improve the stress on the upper and lower edges of the main beam. After the external prestressed reinforcement, the ratio of the observed value to the observed value in the filed load test of the cable-stayed bridge's decreased significantly. It is up to 31% increase in bending capacity of main beams and up to 24% increase in stiffness. This article is instructive for the reinforcement of the early-built sparse-cable reinforced concrete cable-stayed bridge, while also expanding the scope of implementation of external prestressed reinforcement technology
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