1,034 research outputs found
Many-body Green's function theory of ferromagnetic Heisenberg systems with single-ion anisotropies in more than one direction
The behaviour of ferromagnetic systems with single-ion anisotropies in more
than one direction is investigated with many-body Green's function theory
generalizing earlier work with uniaxial anisotropies only. It turns out to be
of advantage to construct Green's functions in terms of the spin operators S^x,
S^y and S^z, instead of the commonly used S^+,S^- and S^z operators. The
exchange energy terms are decoupled by RPA and the single-ion anisotropy terms
by a generalization of the Anderson-Callen decoupling. We stress that in the
derivation of the formalism none of the three spatial axes is special, so that
one is always able to select a reference direction along which a magnetization
component is not zero. Analytical expressions are obtained for all three
components of the magnetization and the expectation values ,
and for any spin quantum number S. The formalism considers both
in-plane and out-of-plane anisotropies. Numerical calculations illustrate the
behaviour of the magnetization for 3-dimensional and 2-dimensional systems for
various parameters. In the 2-dimensional case, the magnetic dipole-dipole
coupling is included, and a comparison is made between in-plane and
out-of-plane anisotropies.Comment: 16 pages, 8 figures, missing figures adde
Direct Force Measurements During Transient Flow about Pitching Flat Plates
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143125/1/6.2017-0995.pd
Charge Ordered RVB States in the Doped Cuprates
We study charge ordered d-wave resonating valence bond states (dRVB) in the
doped cuprates, and estimate the energies of these states in a generalized model by using a renormalized mean field theory. The long range Coulomb
potential tends to modulate the charge density in favor of the charge ordered
RVB state. The possible relevance to the recently observed
checkerboard patterns in tunnelling conductance in high cuprates is
discussed.Comment: 4 pages, 4 figures, 3 table
Electromagnetic Radiation from a Spherical Static Current Source Coupled to Harmonic Axion Field
The electromagnetic fields generated from a static current source on a spherical surface are calculated in the framework of axion electrodynamics to first order in the coupling parameter. Comparisons of the results are made with reference to various results obtained in conventional Maxwell electrodynamics, as well as previous results obtained for point magnetic dipole source coupled to harmonic axion fields. Distinct features from the results so obtained are highlighted for possible experimental probing of the axions via electromagnetic interactions. In particular, electromagnetic radiation from sources with strong magnetic field is studied which may enable the detection of a cosmic axion field from its interaction with objects like neutron stars
Effects of Planform Geometry and Pivot Axis Location on the Aerodynamics of Pitching Low Aspect Ratio Wings
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106469/1/AIAA2013-2992.pd
Green Nanochemistry:Metal Oxide Nanoparticles and Porous Thin Films from Bare Metal Powders
Cataloged from PDF version of article.A universal, simple, robust, widely applicable and cost-effective aqueous process is described for a controlled oxidative dissolution process of micrometer-sized metal powders to form high-purity aqueous dispersions of colloidally stable 3-8 nm metal oxide nanoparticles. Their utilization for making single and multilayer optically transparent high-surface-area nanoporous films is demonstrated. This facile synthesis is anticipated to find numerous applications in materials science, engineering, and nanomedicine. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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