29 research outputs found
Multicone Diamond Waveguides for Nanoscale Quantum Sensing
The long-lived electronic spin of the nitrogen-vacancy (NV) center in diamond
is a promising quantum sensor for detecting nanoscopic magnetic and electric
fields in a variety of experimental conditions. Nevertheless, an outstanding
challenge in improving measurement sensitivity is the poor signal-to-noise
ratio (SNR) of prevalent optical spin-readout techniques. Here, we address this
limitation by coupling individual NV centers to optimized diamond nanopillar
structures, thereby improving optical collection efficiency of fluorescence.
First, we optimize the structure in simulation, observing an increase in
collection efficiency for tall ( 5 m) pillars with tapered
sidewalls. We subsequently verify these predictions by fabricating and
characterizing a representative set of structures using a reliable and
reproducible nanofabrication process. An optimized device yields increased SNR,
owing to improvements in collimation and directionality of emission.
Promisingly, these devices are compatible with low-numerical-aperture,
long-working-distance collection optics, as well as reduced tip radius,
facilitating improved spatial resolution for scanning applications.Comment: 22 pages, five figure
Time-resolved imaging of pulse-induced magnetization reversal with a microwave assist field
The reversal of the magnetization under the influence of a field pulse has
been previously predicted to be an incoherent process with several competing
phenomena such as domain wall relaxation, spin wave-mediated instability
regions, and vortex-core mediated reversal dynamics. However, there has been no
study on the direct observation of the switching process with the aid of a
microwave signal input. We report a time-resolved imaging study of
magnetization reversal in patterned magnetic structures under the influence of
a field pulse with microwave assistance. The microwave frequency is varied to
demonstrate the effect of resonant microwave-assisted switching. We observe
that the switching process is dominated by spin wave dynamics generated as a
result of magnetic instabilities in the structures, and identify the
frequencies that are most dominant in magnetization reversal
The effect of magnetic anisotropy on the spin configurations of patterned La0.7Sr0.3MnO3 elements
International audienceWe study the effect of magnetocrystalline anisotropy on the magnetic configurations of La0:7Sr0:3MnO3 bar and triangle elements using photoemission electron microscopy imaging. The dominant remanent state is a low energy flux-closure state for both thin (15 nm) and thick (50 nm) elements. The magnetocrystalline anisotropy, which competes with the dipolar energy, causes a strong modification of the spin configuration in the thin elements, depending on the shape, size and orientation of the structures. We investigate the magnetic switching processes and observe in triangular shaped elements a displacement of the vortex core along the easy axis for an external magnetic field applied close to the hard axis, which is well reproduced by micromagnetic simulations