12,768 research outputs found
Atomic level micromagnetic model of recording media switching at elevated temperatures
An atomic level micromagnetic model of granular recording media is developed
and applied to examine external field-induced grain switching at elevated
temperatures which captures non-uniform reversal modes. The results are
compared with traditional methods which employ the Landau-Lifshitz-Gilbert
equations based on uniformly magnetized grains with assigned intrinsic
temperature profiles for and . Using nominal parameters
corresponding to high-anisotropy FePt-type media envisioned for Energy Assisted
Magnetic Recording, our results demonstrate that atomic-level reversal slightly
reduces the field required to switch grains at elevated temperatures, but
results in larger fluctuations, when compared to a uniformly magnetized grain
model.Comment: 4 pages, 5 figure
Two Avenues to Self-Interaction Correction within Kohn-Sham Theory: Unitary Invariance is the Shortcut
The most widely-used density functionals for the exchange-correlation energy
are inexact for one-electron systems. Their self-interaction errors can be
severe in some applications. The problem is not only to correct the
self-interaction error, but to do so in a way that will not violate
size-consistency and will not go outside the standard Kohn-Sham density
functional theory. The solution via the optimized effective potential (OEP)
method will be discussed, first for the Perdew-Zunger self-interaction
correction (whose performance for molecules is briefly summarized) and then for
the more modern self-interaction corrections based upon unitarily-invariant
indicators of iso-orbital regions. For the latter approaches, the OEP
construction is greatly simplified. The kinetic-energy-based iso-orbital
indicator \tau^W_\sigma(\re)/\tau_\sigma(\re) will be discussed and plotted,
along with an alternative exchange-based indicator
Caring for country and sustainable Indigenous development: opportunities, constraints and innovation
This paper explores how Indigenous community-based natural resource management can generate both conservation benefit and economic development opportunity. We begin by noting that much of the Indigenous estate in north Australia is either thinly populated or unpopulated. There is emerging evidence that, in situations where Indigenous people live on their country, ecological and wider benefits are generated via favourable fire regimes, control over weed infestations, and potentially through feral animal harvesting. When people are on country, they generate economic benefit for themselves by harvesting wildlife for consumption and engage with the market sector by using natural resources in commercial enterprise like arts and crafts production. We argue that there is a strong correlation between such activities and cost-effective natural resource management. Links between landcare, wildlife use and biodiversity conservation need to be recognized, celebrated and supported. The removal of many barriers to enhanced and innovative Indigenous participation in such activities, and equitable public support through programs like Landcare, will facilitate sustainable economic development options that are compatible with Indigenous priorities, while ameliorating Indigenous disadvantage
Micromagnetic simulations of sweep-rate dependent coercivity in perpendicular recording media
The results of micromagnetic simulations are presented which examine the
impact of thermal fluctuations on sweep rate dependent coercivities of both
single-layer and exchange-coupled-composite (ECC) perpendicular magnetic
recording media. M-H loops are calculated at four temperatures and sweep rates
spanning five decades with fields applied normal to the plane and at 45
degrees. The impact of interactions between grains is evaluated. The results
indicate a significantly weaker sweep-rate dependence for ECC media suggesting
more robustness to long-term thermal effects. Fitting the modeled results to
Sharrock-like scaling proposed by Feng and Visscher [J. Appl. Phys. 95, 7043
(2004)] is successful only in the case of single-layer media with the field
normal to the plane.Comment: 7 pages, 14 figure
Lipkin translational-symmetry restoration in the mean-field and energy-density-functional methods
Based on the 1960 idea of Lipkin, the minimization of energy of a
symmetry-restored mean-field state is equivalent to the minimization of a
corrected energy of a symmetry-broken state with the Peierls-Yoccoz mass. It is
interesting to note that the "unphysical" Peierls-Yoccoz mass, and not the true
mass, appears in the Lipkin projected energy. The Peierls-Yoccoz mass can be
easily calculated from the energy and overlap kernels, which allows for a
systematic, albeit approximate, restoration of translational symmetry within
the energy-density formalism. Analogous methods can also be implemented for all
other broken symmetries.Comment: 15 LaTeX pages, 8 eps figures, submitted to Journal of Physics
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