976 research outputs found
Electronic structure of fully epitaxial Co2TiSn thin films
In this article we report on the properties of thin films of the full Heusler
compound Co2TiSn prepared by DC magnetron co-sputtering. Fully epitaxial,
stoichiometric films were obtained by deposition on MgO (001) substrates at
substrate temperatures above 600{\deg}C. The films are well ordered in the L21
structure, and the Curie temperature exceeds slightly the bulk value. They show
a significant, isotropic magnetoresistance and the resistivity becomes strongly
anomalous in the paramagnetic state. The films are weakly ferrimagnetic, with
nearly 1 \mu_B on the Co atoms, and a small antiparallel Ti moment, in
agreement with theoretical expectations. From comparison of x-ray absorption
spectra on the Co L3/L2 edges, including circular and linear magnetic
dichroism, with ab initio calculations of the x-ray absorption and circular
dichroism spectra we infer that the electronic structure of Co2TiSn has
essentially non-localized character. Spectral features that have not been
explained in detail before, are explained here in terms of the final state band
structure.Comment: 11 pages, 8 figure
Repeat or not repeat?—Statistical validation of tandem repeat prediction in genomic sequences
Tandem repeats (TRs) represent one of the most prevalent features of genomic sequences. Due to their abundance and functional significance, a plethora of detection tools has been devised over the last two decades. Despite the longstanding interest, TR detection is still not resolved. Our large-scale tests reveal that current detectors produce different, often nonoverlapping inferences, reflecting characteristics of the underlying algorithms rather than the true distribution of TRs in genomic data. Our simulations show that the power of detecting TRs depends on the degree of their divergence, and repeat characteristics such as the length of the minimal repeat unit and their number in tandem. To reconcile the diverse predictions of current algorithms, we propose and evaluate several statistical criteria for measuring the quality of predicted repeat units. In particular, we propose a model-based phylogenetic classifier, entailing a maximum-likelihood estimation of the repeat divergence. Applied in conjunction with the state of the art detectors, our statistical classification scheme for inferred repeats allows to filter out false-positive predictions. Since different algorithms appear to specialize at predicting TRs with certain properties, we advise applying multiple detectors with subsequent filtering to obtain the most complete set of genuine repeat
Recommended from our members
Direct imaging of long-range ferromagnetic and antiferromagnetic order in a dipolar metamaterial
Magnetic metamaterials such as artificial spin ice offer a route to tailor magnetic properties. Such materials can be fabricated by lithographically defining arrays of nanoscale magnetic islands. The magnetostatic interactions between the elements are influenced by their shape and geometric arrangement and can lead to long-range ordering. We demonstrate how the magnetic order in a two-dimensional periodic array of circular disks is controlled by the lattice symmetry. Antiferromagnetic and ferromagnetic order extending through the entire array is observed for the square and hexagonal lattice, respectively. Furthermore, we show that a minute deviation from perfect circularity of the elements along a preferred direction results in room-temperature blocking and favors collinear spin textures
Green consumer markets in the fight against climate change
Climate change has become one of the greatest threats to environmental security, as attested by the growing frequency of severe flooding and storms, extreme temperatures and droughts. Accordingly, the European Union’s (EU) 6th Environment Action Programme (2010) lists tackling climate change as its first priority. A key aim of the EU has been to cut CO2 emissions, a major factor in climate change, by 8% until 2012 and 20% until 2020. The European Commission has proposed the encouragement of private consumer market for green products and services as one of several solutions to this problem. However, existing research suggests that the market share of these products has been only 3%, although 30% of individuals favour environmental and ethical goods. This article uses Public Goods Theory to explain why the contribution of the green consumer market to fighting climate change has been and possibly may remain limited without further public intervention
Loop Bifurcation and Magnetization Rotation in Exchange Biased Ni/FeF2
Exchange biased Ni/ FeF2 films have been investigated using vector coil
vibrating sample magnetometry as a function of the cooling field strength H_FC.
In films with epitaxial FeF2, a loop bifurcation develops with increasing H_FC
as it divides into two sub-loops shifted oppositely from zero field by the same
amount. The positively biased sub-loop grows in size with H_FC until only a
single positively shifted loop is found. Throughout this process, the
negative/positive (sub)loop shift has maintained the same discrete value. This
is in sharp contrast to films with twinned FeF2 where the exchange field
gradually changes with increasing H_FC. The transverse magnetization shows
clear correlations with the longitudinal sub-loops. Interestingly, over 85% of
the Ni reverses its magnetization by rotation, either in one step or through
two successive rotations. These results are due to the single crystal nature of
the antiferromagnetic FeF2, which breaks down into two opposite regions of
large domains.Comment: 16 pages, 3 figures, to appear in PR
Towards diluted magnetism in TaAs
Magnetism in Weyl semimetals is desired to investigate the interaction
between the magnetic moments and Weyl fermions, e.g. to explore anomalous
quantum Hall phenomena. Here we demonstrate that proton irradiation is an
effective tool to induce ferromagnetism in the Weyl semimetal TaAs. The
intrinsic magnetism is observed with a transition temperature above room
temperature. The magnetic moments from d states are found to be localized
around Ta atoms. Further, the first-principles calculations indicate that the d
states localized on the nearest-neighbor Ta atoms of As vacancy sites are
responsible for the observed magnetic moments and the long-ranged magnetic
order. The results show the feasibility of inducing ferromagnetism in Weyl
semimetals so that they may facilitate the applications of this material in
spintronics.Comment: 20 pages, 6 figure
- …