887 research outputs found
Ferromagnetic resonance force microscopy on a thin permalloy film
Ferromagnetic Resonance Force Microscopy (FMRFM) offers a means of performing
local ferromagnetic resonance. We have studied the evolution of the FMRFM force
spectra in a continuous 50 nm thick permalloy film as a function of probe-film
distance and performed numerical simulations of the intensity of the FMRFM
probe-film interaction force, accounting for the presence of the localized
strongly nonuniform magnetic field of the FMRFM probe magnet. Excellent
agreement between the experimental data and the simulation results provides
insight into the mechanism of FMR mode excitation in an FMRFM experiment.Comment: 9 pages, 2 figure
Planetary Science Goals for the Spitzer Warm Era
The overarching goal of planetary astronomy is to deduce how the present collection of objects found in our Solar System were formed from the original material present in the proto-solar nebula. As over two hundred exo-planetary systems are now known, and multitudes more are expected, the Solar System represents the closest and best system which we can study, and the only one in which we can clearly resolve individual bodies other than planets. In this White Paper we demonstrate how to use Spitzer Space Telescope InfraRed Array Camera Channels 1 and 2 (3.6 and 4.5 µm) imaging photometry with large dedicated surveys to advance our knowledge of Solar System formation and evolution. There are a number of vital, key projects to be pursued using dedicated large programs that have not been pursued during the five years of Spitzer cold operations. We present a number of the largest and most important projects here; more will certainly be proposed once the warm era has begun, including important observations of newly discovered objects
On the Liaison Between Superconductivity and Phase Separation
Models of strongly correlated electrons that tend to phase separate are
studied including a long-range 1/r repulsive interaction. It is observed that
charge-density-wave states become stable as the strength of the 1/r term, , is increased. Due to this effect, the domain of stability of the
superconducting phases that appear near phase separation at is not enlarged by a 1/r interaction as naively expected. Nevertheless,
superconductivity exists in a wide region of parameter space, even if phase
separation is suppressed. Our results have implications for some theories of
the cuprates.Comment: 11 pages, 9 postscript figures are appende
On the Spectrum of Field Quadratures for a Finite Number of Photons
The spectrum and eigenstates of any field quadrature operator restricted to a
finite number of photons are studied, in terms of the Hermite polynomials.
By (naturally) defining \textit{approximate} eigenstates, which represent
highly localized wavefunctions with up to photons, one can arrive at an
appropriate notion of limit for the spectrum of the quadrature as goes to
infinity, in the sense that the limit coincides with the spectrum of the
infinite-dimensional quadrature operator. In particular, this notion allows the
spectra of truncated phase operators to tend to the complete unit circle, as
one would expect. A regular structure for the zeros of the Christoffel-Darboux
kernel is also shown.Comment: 16 pages, 11 figure
Origin of four-fold anisotropy in square lattices of circular ferromagnetic dots
We discuss the four-fold anisotropy of in-plane ferromagnetic resonance (FMR)
field , found in a square lattice of circular Permalloy dots when the
interdot distance gets comparable to the dot diameter . The minimum
, along the lattice axes,
differ by 50 Oe at = 1.1. This anisotropy, not expected in
uniformly magnetized dots, is explained by a non-uniform magnetization
\bm(\br) in a dot in response to dipolar forces in the patterned magnetic
structure. It is well described by an iterative solution of a continuous
variational procedure.Comment: 4 pages, 3 figures, revtex, details of analytic calculation and new
references are adde
Nonlinear Meissner Effect in CuO Superconductors
Recent theories of the NMR in the CuO superconductors are based on a
spin-singlet order parameter. Since this state has nodal lines on
the Fermi surface, nonlinear effects associated with low-energy quasiparticles
become important, particularly at low temperatures. We show that the
field-dependence of the supercurrent, below the nucleation field for vortices,
can be used to locate the positions of the nodal lines of an unconventional gap
in momentum space, and hence test the proposed state.Comment: 5 pages (RevTex), 1 figure (postscript file incl.
A Magnetic Resonance Force Microscopy Quantum Computer with Tellurium Donors in Silicon
We propose a magnetic resonance force microscopy (MRFM)-based nuclear spin
quantum computer using tellurium impurities in silicon. This approach to
quantum computing combines the well-developed silicon technology with expected
advances in MRFM.Comment: 9 pages, 1 figur
Spin Lifetime in Small Electron Spin Ensembles Measured by Magnetic Resonance Force Microscopy
Magnetic Resonance Force Microscopy can enable nanoscale imaging of spin
lifetime. We report temperature dependent measurements of the spin correlation
time of the statistical fluctuations of the spin polarization---the
spin noise---of ensembles containing electron spins by this
technique. Magneto-mechanical relaxation due to spin-cantilever coupling was
controlled and spurious mechanisms that can affect the spin correlation time of
the microscopic signal were characterized. These measurements have
ramifications for optimizing spin sensitivity, understanding local spin
dynamics and for nanoscale imaging.Comment: 5 pages, 5 figures, accepted in Phys. Rev. B (Rapid Comm.
Spin Dynamics in the LTT Phase of ~1/8 Doped Single Crystal La_{1.67}Eu_{0.2}Sr_{0.13}CuO_4
We present La and Cu NMR relaxation measurements in single crystal
La_{1.67}Eu_{0.2}Sr_{0.13}CuO_4. A strong peak in the La spin-lattice
relaxation rate observed in the spin ordered state is well-described by the BPP
mechanism[1] and arises from continuous slowing of electronic spin fluctuations
with decreasing temperature; these spin fluctuations exhibit XY-like anisotropy
in the ordered state. The spin pseudogap is enhanced by the static
charge-stripe order in the LTT phase.Comment: Four pages, three figure
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