Magnetism in two-dimensional materials is not only of fundamental scientific interest but also a promising candidate for numerous applications. However, studies so far, especially the experimental ones, have been mostly limited to the magnetism arising from defects, vacancies, edges or chemical dopants which are all extrinsic effects. Here, we report on the observation of intrinsic antiferromagnetic ordering in the two-dimensional limit. By monitoring the Raman peaks that arise from zone folding due to antiferromagnetic ordering at the transition temperature, we demonstrate that FePS3 exhibits an Ising-type antiferromagnetic ordering down to the monolayer limit, in good agreement with the Onsager solution for two-dimensional order-disorder transition.The transition temperature remains almost independent of the thickness from bulk to the 2 monolayer limit with TN ~118 K, indicating that the weak interlayer interaction has little effect on the antiferromagnetic ordering. KEYWORDSIsing model, Antiferromagentism, Magnetic ordering in 2 Dimension, FePS3, Iron phosphorus trisulfide, Raman spectroscopy 3 Magnetism has played an important role in advancing our understanding of the quantum nature of materials. Especially, low-dimensional magnetism has been a fertile playground, in which novel physical concepts have been learned and thereby moved the frontiers of the modern understanding of materials science. Most of the three-dimensional magnetic systems, other than some exceptional cases of quantum spin and/or strong frustration, host a magnetic order. On the other hand, fluctuations are so strong and easily destroy stabilization of order parameters in onedimensional systems as pointed out in the seminal work by Bethe. 1 Two-dimensional (2D) systems, on the other hand, have attracted much attention because the presence or absence of long-range order depends on the type of spin-spin interactions, which themselves compete with intrinsic fluctuations of either quantum and/or thermal nature.The XXZ Hamiltonian reads 2 ( )where XY J and I J are spin-exchange energies on the basal plane and along the c-axis, respectively; using an order-converting dual transformation that unlike the 1D system there is a phase transition at a finite temperature in the 2D Ising system. 4 Therefore, ferromagnetic or antiferromagnetic ordering in the 2D limit is possible only in the Ising model. There has been some indirect test of this prediction including the most notable one by Kim and Chan using CH4 molecules adsorbed 4 on graphite. 5 However, despite its fundamental importance, there has been no experimental work using a real 2D magnetic material.2D van der Waals (vdW) materials could be an ideal system for the study of 2D magnetism. 6 Unfortunately, however, finding suitable vdW materials and producing atomically thin magnetic materials have been a challenge. Although there have been a few reports of producing atomically thin samples of magnetic materials, 7-10 observation of magnetic ordering in the atomically thin limit has been l...

The main obstacle to weakly supervised semantic image segmentation is the difficulty of obtaining pixel-level information from coarse image-level annotations. Most methods based on image-level annotations use localization maps obtained from the classifier, but these only focus on the small discriminative parts of objects and do not capture precise boundaries. FickleNet explores diverse combinations of locations on feature maps created by generic deep neural networks. It selects hidden units randomly and then uses them to obtain activation scores for image classification. Fick-leNet implicitly learns the coherence of each location in the feature maps, resulting in a localization map which identifies both discriminative and other parts of objects. The ensemble effects are obtained from a single network by selecting random hidden unit pairs, which means that a variety of localization maps are generated from a single image. Our approach does not require any additional training steps and only adds a simple layer to a standard convolutional neural network; nevertheless it outperforms recent comparable techniques on the Pascal VOC 2012 benchmark in both weakly and semi-supervised settings.

How a certain ground state of complex physical systems emerges, especially in two-dimensional materials, is a fundamental question in condensed-matter physics. A particularly interesting case is systems belonging to the class of XY Hamiltonian where the magnetic order parameter of conventional nature is unstable in two-dimensional materials leading to a Berezinskii−Kosterlitz−Thouless transition. Here, we report how the XXZ-type antiferromagnetic order of a magnetic van der Waals material, NiPS3, behaves upon reducing the thickness and ultimately becomes unstable in the monolayer limit. Our experimental data are consistent with the findings based on renormalization-group theory that at low temperatures a two-dimensional XXZ system behaves like a two-dimensional XY one, which cannot have a long-range order at finite temperatures. This work provides the experimental examination of the XY magnetism in the atomically thin limit and opens opportunities of exploiting these fundamental theorems of magnetism using magnetic van der Waals materials.

Findings confirm improved speech perception performance in noise for listeners with hearing impairment when visual input is provided using a transparent surgical mask. Most importantly, the use of the transparent mask did not negatively affect speech perception performance in noise.