83 research outputs found
Polymerization in magnetic metamaterials
We numerically study a mesoscopic system consisting of magnetic nanorings in
the presence of thermal magnetization fluctuations. We find the formation of
dipolar-field-mediated ``bonds" promoting the formation of annuli clusters,
where the amount of bonds between two rings varies between zero and two. This
system resembles the formation of polymers from artificial atoms, which in our
case are the annuli and where the valency of the atom is set by the ring
multipolarity. We investigate the thermodynamic properties of the resulting
structures, and find a transition associated with the formation of the bonds.
In addition, we find that the system has a tendency to form topological
structures, with a distinct critical temperature in relation to the one for
bond formation
GENL: An extensible fitting program for Laue oscillations
GenL is a flexible program that can be used to simulate and/or fit x-ray
diffraction data from epitaxial thin films exhibiting Laue oscillations. It
utilizes differential evolution within a genetic algorithm for the fitting of
data and is based on the kinematic theory of diffraction. Effects of
polarization, absorption, the Lorentz factor, as well as instrumental
resolution and lattice vibrations are taken into account. Useful parameters
that can be extracted after fitting include: atomic interplanar spacings,
number of coherently scattering atomic planes, strain profiles along the film
thickness, and crystal roughness. The program has been developed in MATLAB and
employs a graphical user interface. The deployment strategy is twofold whereby
the software can either be obtained in source code form and executed within the
MATLAB environment, or as a pre-compiled binary for those who prefer not to run
it within MATLAB. Finally, GenL can be easily extended to simulate multilayered
film systems, superlattices, and films with atomic steps. The program is
released under the GNU General Public Licence.Comment: 9 pages, 7 figure
The impact of nanoscale compositional variation on the properties of amorphous alloys
The atomic distribution in amorphous FeZr alloys is found to be close to random, nevertheless, the composition can not be viewed as being homogenous at the nm-scale. The spatial variation of the local composition is identified as the root of the unusual magnetic properties in amorphous Fe1-xZr alloys. The findings are discussed and generalised with respect to the physical properties of amorphous and crystalline materials
Optically Induced Ferromagnetic Order in a Ferrimagnet
The parallel or antiparallel arrangement of electron spins plays a pivotal
role in determining the properties of a physical system. To meet the demands
for innovative technological solutions, extensive efforts have been dedicated
to exploring effective methods for controlling and manipulating this
arrangement [1]. Among various techniques, ultrashort laser pulses have emerged
as an exceptionally efficient tool to influence magnetic order. Ultrafast
suppression of the magnetic order [2,3], all-optical magnetization switching
[4, 5, 6, 7], and light-induced magnetic phase transitions [8] are just a few
notable examples. However, the transient nature of light-induced changes in the
magnetic state has been a significant limitation, hindering their practical
implementation. In this study, we demonstrate that infrared ultrashort laser
pulses can induce a ferromagnetic arrangement of magnetic moments in an
amorphous TbCo alloy, a material that exhibits ferrimagnetism under equilibrium
conditions. Strikingly, the observed changes in the magnetic properties persist
for significantly longer durations than any previously reported findings. Our
results reveal that ultrashort optical pulses can generate materials with
identical chemical composition and structural state but entirely distinct
magnetic arrangements, leading to unique magnetic properties. This breakthrough
discovery marks a new era in light-driven control of matter, offering the
exciting potential to create materials with properties that were once
considered unattainable
Nanoscale magnetophotonics
This Perspective surveys the state-of-the-art and future prospects of science
and technology employing the nanoconfined light (nanophotonics and
nanoplasmonics) in combination with magnetism. We denote this field broadly as
nanoscale magnetophotonics. We include a general introduction to the field and
describe the emerging magneto-optical effects in magnetoplasmonic and
magnetophotonic nanostructures supporting localized and propagating plasmons.
Special attention is given to magnetoplasmonic crystals with transverse
magnetization and the associated nanophotonic non-reciprocal effects, and to
magneto-optical effects in periodic arrays of nanostructures. We give also an
overview of the applications of these systems in biological and chemical
sensing, as well as in light polarization and phase control. We further review
the area of nonlinear magnetophotonics, the semiconductor spin-plasmonics, and
the general principles and applications of opto-magnetism and nano-optical
ultrafast control of magnetism and spintronics
Influence of misfit strain on the physical properties of Fe thin films
We investigate the growth of thin Fe layers on MgAlO (001) and MgO
(001) substrates using dc magnetron sputtering. The crystal quality of Fe
layers deposited on MgAlO is found to be substantially higher as
compared to Fe grown on MgO substrates. The effects of the crystal quality on
the magnetic and electric transport properties are discussed.Comment: 8 pages, 6 figure
Observation of the nonlinear Wood's anomaly on periodic arrays of nickel nanodimers
Linear and nonlinear magneto-photonic properties of periodic arrays of nickel
nanodimers are governed by the interplay of the (local) optical response of
individual nanoparticles and (non-local) diffraction phenomena, with a striking
example of Wood's anomaly. Angular and magnetic-field dependencies of the
second harmonic intensity evidence Wood's anomaly when new diffraction orders
emerge. Near-infrared spectroscopic measurements performed at different optical
wavelengths and grating constants discriminate between the linear and nonlinear
excitation mechanisms of Wood's anomalies. In the nonlinear regime the Wood's
anomaly is characterized by an order-of-magnitude larger effect in intensity
redistribution between the diffracted beams, as compared to the linear case.
The nonlinear Wood's anomaly manifests itself also in the nonlinear magnetic
contrast highlighting the prospects of nonlinear magneto-photonics.Comment: 8 pages, 6 figure
Plasmon-enhanced optical control of magnetism at the nanoscale via the inverse Faraday effect
The relationship between magnetization and light has been the subject of
intensive research for the past century, focusing on the impact of magnetic
moments on light polarization. Conversely, the manipulation of magnetism
through polarized light is being investigated to achieve all-optical control of
magnetism in spintronics. While remarkable discoveries such as single pulse
all-optical switching of the magnetization in thin films and sub-micrometer
structures have been reported, the demonstration of local optical control of
magnetism at the nanoscale has remained elusive. Here, we show that exciting
gold nanodiscs with circularly polarized femtosecond laser pulses leads to the
generation of sizeable local magnetic fields that enable ultrafast local
control of the magnetization of an adjacent magnetic film. In addition, we find
that the highest magnetic fields are generated when exciting the sample at a
wavelength larger than that of the actual plasmonic resonance of the gold
nanodiscs, so avoiding undesired heating effects due to absorption. Our study
paves the way for light-driven control in nanoscale spintronic devices and
provides important insights into the generation of magnetic fields in plasmonic
nanostructures
Magnetic order and energy-scale hierarchy in artificial spin ice
In order to explain and predict the properties of many physical systems, it
is essential to understand the interplay of different energy-scales. Here we
present investigations of the magnetic order in thermalised artificial spin ice
structures, with different activation energies of the interacting Ising-like
elements. We image the thermally equilibrated magnetic states of the
nano-structures using synchrotron-based magnetic microscopy. By comparing
results obtained from structures with one or two different activation energies,
we demonstrate a clear impact on the resulting magnetic order. The differences
are obtained by the analysis of the magnetic spin structure factors, in which
the role of the activation energies is manifested by distinct short-range
order. This demonstrates that artificial spin systems can serve as model
systems, allowing the definition of energy-scales by geometrical design and
providing the backdrop for understanding their interplay.Comment: 8 pages, 5 figures (+ supplementary 6 pages, 4 figures
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