2,213 research outputs found
Sensitivity and spatial resolution for electron-spin-resonance detection by magnetic resonance force microscopy
The signal intensity of electron spin resonance in magnetic resonance force microscopy (MRFM) experiments employing periodic saturation of the electron spin magnetization is determined by four parameters: the rf field H1, the modulation level of the bias field Hm, the spin relaxation time tau1, and the magnetic size R([partial-derivative]H/[partial-derivative]z) of the sample. Calculations of the MRFM spectra obtained from a 2,2-diphenyl-1-picrylhydrazyl particle have been performed for various conditions. The results are compared with experimental data and excellent agreement is found. The systematic variation of the signal intensity as a function of H1 and Hm provides a powerful tool to characterize the MRFM apparatus
Ferromagnetic resonance force microscopy on microscopic cobalt single layer films
We report mechanical detection of ferromagnetic resonance signals from
microscopic Co single layer thin films using a magnetic resonance force
microscope (MRFM). Variations in the magnetic anisotropy field and the
inhomogeneity of were clearly observed in the FMR spectra of microscopic Co
thin films 500 and 1000 angstrom thick and 40 X 200 micron^2 in lateral extent.
This demonstrates the important potential that MRFM detection of FMR holds for
microscopic characterization of spatial distribution of magnetic properties in
magnetic layered materials and devices.Comment: 4 pages, 2 figures, RevTex. To be published in Applied Physics
Letters, October 5, 199
Seeing Double at Neptune's South Pole
Keck near-infrared images of Neptune from UT 26 July 2007 show that the cloud
feature typically observed within a few degrees of Neptune's south pole had
split into a pair of bright spots. A careful determination of disk center
places the cloud centers at -89.07 +/- 0 .06 and -87.84 +/- 0.06 degrees
planetocentric latitude. If modeled as optically thick, perfectly reflecting
layers, we find the pair of features to be constrained to the troposphere, at
pressures greater than 0.4 bar. By UT 28 July 2007, images with comparable
resolution reveal only a single feature near the south pole. The changing
morphology of these circumpolar clouds suggests they may form in a region of
strong convection surrounding a Neptunian south polar vortex.Comment: 10 pages, 7 figures; accepted to Icaru
Stability Properties of Nonhyperbolic Chaotic Attractors under Noise
We study local and global stability of nonhyperbolic chaotic attractors
contaminated by noise. The former is given by the maximum distance of a noisy
trajectory from the noisefree attractor, while the latter is provided by the
minimal escape energy necessary to leave the basin of attraction, calculated
with the Hamiltonian theory of large fluctuations. We establish the important
and counterintuitive result that both concepts may be opposed to each other.
Even when one attractor is globally more stable than another one, it can be
locally less stable. Our results are exemplified with the Holmes map, for two
different sets of parameter, and with a juxtaposition of the Holmes and the
Ikeda maps. Finally, the experimental relevance of these findings is pointed
out.Comment: Phys.Rev. Lett., to be publishe
Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy
Lateral one-dimensional imaging of cobalt (Co) films by means of microscopic ferromagnetic resonance (FMR) detected using the magnetic resonance force microscope (MRFM) is demonstrated. A novel approach involving scanning a localized magnetic probe is shown to enable FMR imaging in spite of the broad resonance linewidth. We introduce a spatially selective local field by means of a small, magnetically polarized spherical crystallite of yttrium iron garnet (YIG). Using MRFM-detected FMR signals from a sample consisting of two Co films, we can resolve the ∼20 μm lateral separation between the films. The results can be qualitatively understood by consideration of the calculated spatial profiles of the magnetic field generated by the YIG sphere
- …