3,725 research outputs found
Quantitative Decoding of Interactions in Tunable Nanomagnet Arrays Using First Order Reversal Curves
To develop a full understanding of interactions in nanomagnet arrays is a
persistent challenge, critically impacting their technological acceptance. This
paper reports the experimental, numerical and analytical investigation of
interactions in arrays of Co nanoellipses using the first-order reversal curve
(FORC) technique. A mean-field analysis has revealed the physical mechanisms
giving rise to all of the observed features: a shift of the non-interacting
FORC-ridge at the low-H end off the local coercivity H axis; a stretch
of the FORC-ridge at the high-H end without shifting it off the H axis;
and a formation of a tilted edge connected to the ridge at the low-H end.
Changing from flat to Gaussian coercivity distribution produces a negative
feature, bends the ridge, and broadens the edge. Finally, nearest neighbor
interactions segment the FORC-ridge. These results demonstrate that the FORC
approach provides a comprehensive framework to qualitatively and quantitatively
decode interactions in nanomagnet arrays.Comment: 19 pages, 4 figures. 9 page supplemental material including 3 figure
Pseudo Spin Valves Using a (112)-textured DO_22 MnGa Fixed Layer
We demonstrate pseudo spin valves with a (112)-textured DO_22 MnGa (MnGa)
tilted magnetization fixed layer and an in-plane CoFe free layer. Single D0_22
MnGa films exhibit a small magnetoresistance (MR) typically observed in metals.
In MnGa/Cu/ CoFe spin valves a transition from a negative (-0.08%) to positive
(3.88%) MR is realized by introducing a thin spin polarizing CoFe insertion
layer at the MnGa/Cu interface and tailoring the MnGa thickness. Finally, the
exchange coupling between the MnGa and CoFe insertion layer is studied using a
first-order reversal curve (FORC) technique.Comment: 5 pages, 4 figures, submitted to IEEE Magnetics Letter
Sex-biased gene expression is repeatedly masculinized in asexual females.
Males and females feature strikingly different phenotypes, despite sharing most of their genome. A resolution of this apparent paradox is through differential gene expression, whereby genes are expressed at different levels in each sex. This resolution, however, is likely to be incomplete, leading to conflict between males and females over the optimal expression of genes. Here we test the hypothesis that gene expression in females is constrained from evolving to its optimum level due to sexually antagonistic selection on males, by examining changes in sex-biased gene expression in five obligate asexual species of stick insect, which do not produce males. We predicted that the transcriptome of asexual females would be feminized as asexual females do not experience any sexual conflict. Contrary to our prediction we find that asexual females feature masculinized gene expression, and hypothesise that this is due to shifts in female optimal gene expression levels following the suppression of sex
Quantum-well states in ultrathin Ag(111) films deposited onto H-passivated Si(111)-(1x1) surfaces
Ag(111) films were deposited at room temperature onto H-passivated
Si(111)-(1x1) substrates, and subsequently annealed at 300 C. An abrupt
non-reactive Ag/Si interface is formed, and very uniform non-strained Ag(111)
films of 6-12 monolayers have been grown. Angle resolved photoemission
spectroscopy has been used to study the valence band electronic properties of
these films. Well-defined Ag sp quantum-well states (QWS) have been observed at
discrete energies between 0.5-2eV below the Fermi level, and their dispersions
have been measured along the GammaK, GammaMM'and GammaL symmetry directions.
QWS show a parabolic bidimensional dispersion, with in-plane effective mass of
0.38-0.50mo, along the GammaK and GammaMM' directions, whereas no dispersion
has been found along the GammaL direction, indicating the low-dimensional
electronic character of these states. The binding energy dependence of the QWS
as a function of Ag film thickness has been analyzed in the framework of the
phase accumulation model. According to this model, a reflectivity of 70% has
been estimated for the Ag-sp states at the Ag/H/Si(111)-(1x1) interface.Comment: 6 pages, 6 figures, submitted to Phys. Rev.
Electronic properties and Fermi surface of Ag(111) films deposited onto H-passivated Si(111)-(1x1) surfaces
Silver films were deposited at room temperature onto H-passivated Si(111)
surfaces. Their electronic properties have been analyzed by angle-resolved
photoelectron spectroscopy. Submonolayer films were semiconducting and the
onset of metallization was found at a Ag coverage of 0.6 monolayers. Two
surface states were observed at -point in the metallic films,
with binding energies of 0.1 and 0.35 eV. By measurements of photoelectron
angular distribution at the Fermi level in these films, a cross-sectional cut
of the Fermi surface was obtained. The Fermi vector determined along different
symmetry directions and the photoelectron lifetime of states at the Fermi level
are quite close to those expected for Ag single crystal. In spite of this
concordance, the Fermi surface reflects a sixfold symmetry rather than the
threefold symmetry of Ag single crystal. This behavior was attributed to the
fact that these Ag films are composed by two domains rotated 60.Comment: 9 pages, 8 figures, submitted to Physical Review
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