440 research outputs found
Effect of the laser fluence on the microstructure and the relating magnetic properties of BaFe₁₂O₁₉ films grown on YSZ(111) by PLD for optimized perpendicular recording
High-quality BaFeO (BaM) films with high uniaxial anisotropy fields of H = 17.5 and 18.5 kOe were obtained by pulsed laser deposition (PLD) at two fluences of 1.5 and 5.1 J/cm on YSZ(111) substrate, using a platinum interlayer for reducing lattice mismatch. We demonstrated that the microstructure, morphology, and stoichiometry of the hexaferrite BaFeO films can be affected by raising the corresponding energy per pulse from 25 to 75 mJ. However, we also concluded that the increase of fluence leads to the formation of a non-stoichiometric BaM film through two nucleation steps and an output growth of small grains in addition to the increase of the defect density. In turn, this has contributed to the enhancement of the coercive field from H = 1769 Oe to H = 2166 Oe as it is required for the improvement of perpendicular recording resolution. We found that both the lateral coherent block size and misorientation of mosaic blocks are remarkably affected by the growth kinetics, which itself depends on the energy per pulse. For a deep understanding of the effect of laser fluence on the microstructure, chemical composition, and on the magnetic properties of thin BaM films, the results of complementary methods are combined. These methods comprise high-resolution X-ray diffraction, atomic force microscopy, high-resolution transmission electron microscopy (TEM), scanning TEM combined with energy-dispersive X-ray spectroscopy, and vibrating sample magnetometer
Machine Learning and Computer Vision Techniques in Bee Monitoring Applications
Machine learning and computer vision are dynamically growing fields, which
have proven to be able to solve very complex tasks. They could also be used for
the monitoring of the honeybee colonies and for the inspection of their health
state, which could identify potentially dangerous states before the situation
is critical, or to better plan periodic bee colony inspections and therefore
save significant costs. In this paper, we present an overview of the
state-of-the-art computer vision and machine learning applications used for bee
monitoring. We also demonstrate the potential of those methods as an example of
an automated bee counter algorithm. The paper is aimed at veterinary and
apidology professionals and experts, who might not be familiar with machine
learning to introduce to them its possibilities, therefore each family of
applications is opened by a brief theoretical introduction and motivation
related to its base method. We hope that this paper will inspire other
scientists to use the machine learning techniques for other applications in bee
monitoring
Extraordinary magnetic response of an anisotropic 2D antiferromagnet via site-dilution
A prominent character of two-dimensional magnetic systems is the enhanced
spin fluctuations, which however reduce the ordering temperature. Here we
report that a magnetic field of only one-thousandth of the Heisenberg
superexchange interaction can induce a crossover, which for practical purposes
is the effective ordering transition, at temperatures about 6 times of the Neel
transition in a site-diluted two-dimensional anisotropic quantum
antiferromagnet. Such a strong magnetic response is enabled because the system
directly enters the antiferromagnetically ordered state from the isotropic
disordered state skipping the intermediate anisotropic stage. The underlying
mechanism is achieved on a pseudospin-half square lattice realized in the
[(SrIrO3)1/(SrTiO3)2] superlattice thin film that is designed to linearly
couple the staggered magnetization to external magnetic fields by virtue of the
rotational symmetry-preserving Dzyaloshinskii Moriya interaction. Our model
analysis shows that the skipping of the anisotropic regime despite the finite
anisotropy is due to the enhanced isotropic fluctuations under moderate
dilution
Quasi-2D anomalous Hall Mott insulator of topologically engineered Jeff =1/2 electrons
We investigate an experimental toy-model system of a pseudospin-half
square-lattice Hubbard Hamiltonian in [(SrIrO3)1/(CaTiO3)1] to include both
nontrivial complex hopping and moderate electronic correlation. While the
former induces electronic Berry phases as anticipated from the weak-coupling
limit, the later stabilizes an antiferromagnetic (AFM) Mott insulator ground
state in analogous to the strong-coupling limit. Their combined results in the
real system are found to be an anomalous Hall effect with a non-monotonic
temperature dependence due to the self-competition of the electron-hole pairing
in the Mott state, and an exceptionally large Ising anisotropy that is captured
as a giant magnon gap beyond the superexchange approach. The unusual phenomena
highlight the rich interplay of electronic topology and electronic correlation
in the intermediate-coupling regime that is largely unexplored and challenging
in theoretical modelling.Comment: Accepted by Phys. Rev.
Strain-modulated Slater-Mott crossover of pseudospin-half square-lattice in (SrIrO3)1/ (SrTiO3)1 superlattices
We report on the epitaxial strain-driven electronic and antiferromagnetic
modulations of a pseudospin-half square lattice realized in superlattices of
(SrIrO3)1/(SrTiO3)1. With increasing compressive strain, we find the
low-temperature insulating behavior to be strongly suppressed with a
corresponding systematic reduction of both the Neel temperature and the
staggered moment. However, despite such a suppression, the system remains
weakly insulating above the Neel transition. The emergence of metallicity is
observed under large compressive strain but only at temperatures far above the
N\'eel transition. These behaviors are characteristics of the Slater-Mott
crossover regime, providing a unique experimental model system of the spin-half
Hubbard Hamiltonian with a tunable intermediate coupling strength
Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC
Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe
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