141 research outputs found
Computational Analysis of a Spiral Thermoelectric Nanoantenna for Solar Energy Harvesting Applications
Thermo-electrical nanoantennas have been proposed as an alternative option
for conversion solar energy harvesting applications. In this work, the response
of a spiral broadband antenna has been obtained from numerical and theoretical
simulations perspectives. The results show that this device exhibits a
responsivity of 20mV/W under 117W/cm2, for a single-frequency radiation. We
discuss strategies for enhanced efficiency
Energy-efficient domain wall motion governed by the interplay of helicity-dependent optical effect and spin-orbit torque
Spin-orbit torque provides a powerful means of manipulating domain walls
along magnetic wires. However, the current density required for domain wall
motion is still too high to realize low power devices. Here we experimentally
demonstrate helicity-dependent domain wall motion by combining synchronized
femtosecond laser pulses and short current pulses in Co/Ni/Co ultra-thin film
wires with perpendicular magnetization. Domain wall can remain pinned under one
laser circular helicity while depinned by the opposite circular helicity.
Thanks to the all-optical helicity-dependent effect, the threshold current
density due to spin-orbit torque can be reduced by more than 50%. Based on this
joint effect combining spin-orbit torque and helicity-dependent laser pulses,
an optoelectronic logic-in-memory device has been experimentally demonstrated.
This work enables a new class of low power spintronic-photonic devices beyond
the conventional approach of all-optical switching or all-current switching for
data storage.Comment: 21 pages, 5 figure
Symmetry broken spin reorientation transition in epitaxial MgO/Fe/MgO layers with competing anisotropies
The observation of perpendicular magnetic anisotropy (PMA) at MgO/Fe interfaces boosted the development of spintronic devices based on ultrathin ferromagnetic layers. Yet, magnetization reversal in the standard magnetic tunnel junctions (MTJs) with competing PMA and in-plane anisotropies remains unclear. Here we report on the field induced nonvolatile broken symmetry magnetization reorientation transition from the in-plane to the perpendicular (out of plane) state at temperatures below 50 K. The samples were 10 nm thick Fe in MgO/Fe(100)/MgO as stacking components of V/MgO/Fe/MgO/Fe/Co double barrier MTJs with an area of 20 Ă— 20 ÎĽm2. Micromagnetic simulations with PMA and different second order anisotropies at the opposite Fe/MgO interfaces qualitatively reproduce the observed broken symmetry spin reorientation transition. Our findings open the possibilities to develop multistate epitaxial spintronics based on competing magnetic anisotropies.This work has been supported in part by Spanish MINECO (MAT2015-66000-P, EUIN2017-87474), SPINORBIT (MDM-2014-0377) and Comunidad de Madrid (NANOFRONTMAG-CM
S2013/MIT-2850). C.T. acknowledges “EMERSPIN” grant ID PN-III-P4-ID-PCE-2016-0143, No. UEFISCDI:22/12.07.201
Seebeck Nanoantennas for Infrared Detection and Energy Harvesting Applications
In this letter we introduce a new type of infrared sensor, based on
thermocouple nanoantennas, which enables the energy detection and gathering in
the mid-infrared region. The proposed detector combines the Seebeck effect, as
a transduction mechanism, with the functionalities of the optical antennas for
optical sensing. By using finite-element numerical simulations we evaluate the
performance and optical-to-electrical conversion efficiency of the proposed
device, unveiling its potential for optical sensing and energy harvesting
applications.Comment: 4 pages, 3 figures, Invited paper at EUCAP 201
Light-induced magnetization reversal of high-anisotropy TbCo alloy films
Magnetization reversal using circularly polarized light provides a new way to
control magnetization without any external magnetic field and has the potential
to revolutionize magnetic data storage. However, in order to reach ultra-high
density data storage, high anisotropy media providing thermal stability are
needed. Here, we evidence all-optical magnetization switching for different
TbxCo1-x ferrimagnetic alloy composition and demonstrate all-optical switching
for films with anisotropy fields reaching 6 T corresponding to anisotropy
constants of 3x106 ergs/cm3. Optical magnetization switching is observed only
for alloys which compensation temperature can be reached through sample
heating
Domain-wall motion induced by spin transfer torque delivered by helicity-dependent femtosecond laser
In magnetic wires with perpendicular anisotropy, moving domain with only
current or only circularly polarized light requires a high power. Here, we
propose to reduce it by using both short current pulses and femtosecond laser
pulses simultaneously. The wires were made out of perpendicularly magnetized
film of Pt/Co/Ni/Co/Pt. The displacement of the domain wall is found to be
dependent on the laser helicity. Based on a quantitative analysis of the
current-induced domain wall motion, the spin orbit torque contribution can be
neglected when compared to the spin transfer torque contribution. The effective
field of the spin transfer torque is extracted from the pulsed field domain
wall measurements. Finally, our result can be described using the
Fatuzzo-Labrune model and considering the effective field due to the polarized
laser beam, the effective field due to spin transfer torque, and the Gaussian
temperature distribution of the laser spot.Comment: 14 pages, 4 figure
Fragmentation of magnetism in artificial kagome dipolar spin ice
Geometrical frustration in magnetic materials often gives rise to exotic,
low-temperature states of matter, like the ones observed in spin ices. Here we
report the imaging of the magnetic states of a thermally-active artificial
magnetic ice that reveal the fingerprints of a spin fragmentation process. This
fragmentation corresponds to a splitting of the magnetic degree of freedom into
two channels and is evidenced in both real and reciprocal space. Furthermore,
the internal organization of both channels is interpreted within the framework
of a hybrid spin-charge model that directly emerges from the parent spin model
of the kagome dipolar spin ice. Our experimental and theoretical results
provide insights into the physics of frustrated magnets and deepen our
understanding of emergent fields through the use of tailor-made magnetism.Comment: 9 pages, 5 figures. Published version available on the Nat. Comm. web
site:
http://www.nature.com/ncomms/2016/160513/ncomms11446/full/ncomms11446.htm
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