2,927 research outputs found
Frustration Driven Stripe Domain Formation in Co/Pt Multilayer Films
We report microscopic mechanisms for an unusual magnetization reversal
behavior in Co/Pt multilayers where some of the first-order reversal curves
protrude outside of the major loop. Transmission x-ray microscopy reveals a
fragmented stripe domain topography when the magnetic field is reversed prior
to saturation, in contrast to an interconnected pattern when reversing from a
saturated state. The different domain nucleation and propagation behaviors are
due to unannihilated domains from the prior field sweep. These residual domains
contribute to random dipole fields that impede the subsequent domain growth and
prevent domains from growing as closely together as for the interconnected
pattern.Comment: 13 pages, 3 figures, to appear in AP
Poda e desbaste no cultivo de nogueira-pecã em plantios adensados.
Dissertação (Mestre em Ciências) - Programa de Pós-Graduação em Agronomia da Faculdade de Agronomia Eliseu Maciel, Universidade Federal de Pelotas, Pelotas. Orientador: Carlos Roberto Martins (CPACT); Coorientador: Marcelo Barbosa Malgarim
Using Muonic Hydrogen in Optical Spectroscopy Experiment to Detect Extra Dimensions
Considering that gravitational force might deviate from Newton's
inverse-square law (ISL) and become much stronger in small scale, we propose a
kind of optical spectroscopy experiment to detect this possible deviation and
take electronic, muonic and tauonic hydrogen atoms as examples. This experiment
might be used to indirectly detect the deviation of ISL down to nanometer scale
and to explore the possibility of three extra dimensions in ADD's model, while
current direct gravity tests cannot break through micron scale and go beyond
two extra dimensions scenario.Comment: 9 pages, 2 figures. To appear in IJT
Hysteresis loops of Co-Pt perpendicular magnetic multilayers
We develop a phenomenological model to study magnetic hysteresis in two
samples designed as possible perpendicular recording media. A stochastic
cellular automata model captures cooperative behavior in the nucleation of
magnetic domains. We show how this simple model turns broad hysteresis loops
into loops with sharp drops like those observed in these samples, and explains
their unusual features. We also present, and experimentally verify, predictions
of this model, and suggest how insights from this model may apply more
generally.Comment: 4.5 pages, 5 figure
Field-test of a robust, portable, frequency-stable laser
We operate a frequency-stable laser in a non-laboratory environment where the
test platform is a passenger vehicle. We measure the acceleration experienced
by the laser and actively correct for it to achieve a system acceleration
sensitivity of = /g, /g, and /g for accelerations in three orthogonal
directions at 1 Hz. The acceleration spectrum and laser performance are
evaluated with the vehicle both stationary and moving. The laser linewidth in
the stationary vehicle with engine idling is 1.7(1) Hz
Influence of ion irradiation on switching field and switching field distribution in arrays of Co/Pd-based bit pattern media
International audienceWe have used ion irradiation to tune switching field and switching field distribution ͑SFD͒ in polycrystalline Co/Pd multilayer-based bit pattern media. Light He + ion irradiation strongly decreases perpendicular magnetic anisotropy amplitude due to Co/Pd interface intermixing, while the granular structure, i.e., the crystalline anisotropy, remains unchanged. In dot arrays, the anisotropy reduction leads to a decrease in coercivity ͑H C ͒ but also to a strong broadening of the normalized SFD/ H C ͑in percentage͒, since the relative impact of misaligned grains is enhanced. Our experiment thus confirms the major role of misorientated grains in SFD of nanodevice arrays. Today a major research effort in magnetism is targeted toward achieving ultrahigh density data storage with nano-scale magnets. Spin-transfer magnetic random access memory ͑spin-RAM͒ and bit patterned media ͑BPM͒ technologies are currently part of the most promising media. The implementation of both of these technologies relies on achieving in-detail physical understanding and control of the magnetization reversal mechanism in each nanoscopic individual bit to ensure reproducibility of the bit properties in order to avoid write errors. Perpendicular magnetic anisotropy ͑PMA͒ materials, such as polycrystalline Co/Pd, Co/Pt, and Co/Ni multilayers, are believed to be promising materials for both spin-RAM and BPM applications. 1–4 Indeed, they have a well defined high amplitude uniaxial anisotropy that provides good thermal stability while offering low critical current in spin-transfer devices 2 and tunable switching fields in BPM.
The Threat of Capital Drain: A Rationale for Public Banks?
This paper yields a rationale for why subsidized public banks may be desirable from a regional perspective in a financially integrated economy. We present a model with credit rationing and heterogeneous regions in which public banks prevent a capital drain from poorer to richer regions by subsidizing local depositors, for example, through a public guarantee. Under some conditions, cooperative banks can perform the same function without any subsidization; however, they may be crowded out by public banks. We also discuss the impact of the political structure on the emergence of public banks in a political-economy setting and the role of interregional mobility
Aperfeiçoamento da técnica de criação de adultos de diabrotica speciosa (Coleoptera: Chrysomelidae) em dieta natural.
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