366 research outputs found
Soliton pair dynamics in patterned ferromagnetic ellipses
Confinement alters the energy landscape of nanoscale magnets, leading to the
appearance of unusual magnetic states, such as vortices, for example. Many
basic questions concerning dynamical and interaction effects remain unanswered,
and nanomagnets are convenient model systems for studying these fundamental
physical phenomena. A single vortex in restricted geometry, also known as a
non-localized soliton, possesses a characteristic translational excitation mode
that corresponds to spiral-like motion of the vortex core around its
equilibrium position. Here, we investigate, by a microwave reflection
technique, the dynamics of magnetic soliton pairs confined in lithographically
defined, ferromagnetic Permalloy ellipses. Through a comparison with
micromagnetic simulations, the observed strong resonances in the subgigahertz
frequency range can be assigned to the translational modes of vortex pairs with
parallel or antiparallel core polarizations. Vortex polarizations play a
negligible role in the static interaction between two vortices, but their
effect dominates the dynamics.Comment: supplemental movies on
http://www.nature.com/nphys/journal/v1/n3/suppinfo/nphys173_S1.htm
Controlling of Iridium films using interfacial proximity effects
High precision calorimetry using superconducting transition edge sensors
requires the use of superconducting films with a suitable , depending on
the application. To advance high-precision macrocalorimetry, we require
low- films that are easy to fabricate. A simple and effective way to
suppress of superconducting Iridium through the proximity effect is
demonstrated by using Ir/Pt bilayers as well as Au/Ir/Au trilayers. While Ir/Au
films fabricated by applying heat to the substrate during Ir deposition have
been used in the past for superconducting sensors, we present results of
suppression on Iridium by deposition at room temperature in Au/Ir/Au trilayers
and Ir/Pt bilayers in the range of 20-100~mK. Measurements of the
relative impedance between the Ir/Pt bilayers and Au/Ir/Au trilayers fabricated
show factor of 10 higher values in the Ir/Pt case. These new films could
play a key role in the development of scalable superconducting transition edge
sensors that require low- films to minimize heat capacity and maximize
energy resolution, while keeping high-yield fabrication methods.Comment: 5 journal pages, 4 figure
Low-loss Si-based Dielectrics for High Frequency Components of Superconducting Detectors
Silicon-based dielectric is crucial for many superconducting devices,
including high-frequency transmission lines, filters, and resonators. Defects
and contaminants in the amorphous dielectric and at the interfaces between the
dielectric and metal layers can cause microwave losses and degrade device
performance. Optimization of the dielectric fabrication, device structure, and
surface morphology can help mitigate this problem. We present the fabrication
of silicon oxide and nitride thin film dielectrics. We then characterized them
using Scanning Electron Microscopy, Atomic Force Microscopy, and
spectrophotometry techniques. The samples were synthesized using various
deposition methods, including Plasma-Enhanced Chemical Vapor Deposition and
magnetron sputtering. The films morphology and structure were modified by
adjusting the deposition pressure and gas flow. The resulting films were used
in superconducting resonant systems consisting of planar inductors and
capacitors. Measurements of the resonator properties, including their quality
factor, were performed.Comment: 4 pages, 5 figures, conferenc
SPT-3G: A Next-Generation Cosmic Microwave Background Polarization Experiment on the South Pole Telescope
We describe the design of a new polarization sensitive receiver, SPT-3G, for
the 10-meter South Pole Telescope (SPT). The SPT-3G receiver will deliver a
factor of ~20 improvement in mapping speed over the current receiver, SPTpol.
The sensitivity of the SPT-3G receiver will enable the advance from statistical
detection of B-mode polarization anisotropy power to high signal-to-noise
measurements of the individual modes, i.e., maps. This will lead to precise
(~0.06 eV) constraints on the sum of neutrino masses with the potential to
directly address the neutrino mass hierarchy. It will allow a separation of the
lensing and inflationary B-mode power spectra, improving constraints on the
amplitude and shape of the primordial signal, either through SPT-3G data alone
or in combination with BICEP-2/KECK, which is observing the same area of sky.
The measurement of small-scale temperature anisotropy will provide new
constraints on the epoch of reionization. Additional science from the SPT-3G
survey will be significantly enhanced by the synergy with the ongoing optical
Dark Energy Survey (DES), including: a 1% constraint on the bias of optical
tracers of large-scale structure, a measurement of the differential Doppler
signal from pairs of galaxy clusters that will test General Relativity on ~200
Mpc scales, and improved cosmological constraints from the abundance of
clusters of galaxies.Comment: 21 pages, 9 figures. To be published in Proceedings of SPIE Volume
9153. Presented at SPIE Astronomical Telescopes + Instrumentation 2014,
conference 915
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