76 research outputs found
Ideal Spin Filters: Theoretical Study of Electron Transmission Through Ordered and Disordered Interfaces Between Ferromagnetic Metals and Semiconductors
It is predicted that certain atomically ordered interfaces between some
ferromagnetic metals (F) and semiconductors (S) should act as ideal spin
filters that transmit electrons only from the majority spin bands or only from
the minority spin bands of the F to the S at the Fermi energy, even for F with
both majority and minority bands at the Fermi level. Criteria for determining
which combinations of F, S and interface should be ideal spin filters are
formulated. The criteria depend only on the bulk band structures of the S and F
and on the translational symmetries of the S, F and interface. Several examples
of systems that meet these criteria to a high degree of precision are
identified. Disordered interfaces between F and S are also studied and it is
found that intermixing between the S and F can result in interfaces with spin
anti-filtering properties, the transmitted electrons being much less spin
polarized than those in the ferromagnetic metal at the Fermi energy. A patent
application based on this work has been commenced by Simon Fraser University.Comment: RevTeX, 12 pages, 5 figure
Current-Induced Torques in Magnetic Metals: Beyond Spin Transfer
Current-induced torques on ferromagnetic nanoparticles and on domain walls in
ferromagnetic nanowires are normally understood in terms of transfer of
conserved spin angular momentum between spin-polarized currents and the
magnetic condensate. In a series of recent articles we have discussed a
microscopic picture of current-induced torques in which they are viewed as
following from exchange fields produced by the misaligned spins of current
carrying quasiparticles. This picture has the advantage that it can be applied
to systems in which spin is not approximately conserved. More importantly, this
point of view makes it clear that current-induced torques can also act on the
order parameter of an antiferromagnetic metal, even though this quantity is not
related to total spin. In this informal and intentionally provocative review we
explain this picture and discuss its application to antiferromagnets.Comment: 5 figures, to appear in Journal of Magnetism and
Magnetic Reversal on Vicinal Surfaces
We present a theoretical study of in-plane magnetization reversal for vicinal
ultrathin films using a one-dimensional micromagnetic model with
nearest-neighbor exchange, four-fold anisotropy at all sites, and two-fold
anisotropy at step edges. A detailed "phase diagram" is presented that catalogs
the possible shapes of hysteresis loops and reversal mechanisms as a function
of step anisotropy strength and vicinal terrace length. The steps generically
nucleate magnetization reversal and pin the motion of domain walls. No sharp
transition separates the cases of reversal by coherent rotation and reversal by
depinning of a ninety degree domain wall from the steps. Comparison to
experiment is made when appropriate.Comment: 12 pages, 8 figure
Diverse aging rates in ectothermic tetrapods provide insights for the evolution of aging and longevity
Comparative studies of mortality in the wild are necessary to understand the evolution of aging; yet, ectothermic tetrapods are underrepresented in this comparative landscape, despite their suitability for testing evolutionary hypotheses. We present a study of aging rates and longevity across wild tetrapod ectotherms, using data from 107 populations (77 species) of nonavian reptiles and amphibians. We test hypotheses of how thermoregulatory mode, environmental temperature, protective phenotypes, and pace of life history contribute to demographic aging. Controlling for phylogeny and body size, ectotherms display a higher diversity of aging rates compared with endotherms and include phylogenetically widespread evidence of negligible aging. Protective phenotypes and life-history strategies further explain macroevolutionary patterns of aging. Analyzing ectothermic tetrapods in a comparative context enhances our understanding of the evolution of aging.Animal science
Publisher correction: Synthetic antiferromagnetic spintronics (Nature Physics (2018) DOI: 10.1038/s41567-018-0050-y)
Owing to a technical error, this Perspective was originally published without its received and accepted dates in the HTML version; the dates âReceived: 30 May 2017; Accepted: 17 January 2018â have now been included. The PDF is correct
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