338 research outputs found
Magnetic control of flexible thermoelectric devices based on macroscopic 3D interconnected nanowire networks
Spin-related effects in thermoelectricity can be used to design more
efficient refrigerators and offer novel promising applications for the
harvesting of thermal energy. The key challenge is to design structural and
compositional magnetic material systems with sufficiently high efficiency and
power output for transforming thermal energy into electric energy and vice
versa. Here, the fabrication of large-area 3D interconnected Co/Cu nanowire
networks is demonstrated, thereby enabling the controlled Peltier cooling of
macroscopic electronic components with an external magnetic field. The
flexible, macroscopic devices overcome inherent limitations of nanoscale
magnetic structures due to insufficient power generation capability that limits
the heat management applications. From properly designed experiments, large
spin-dependent Seebeck and Peltier coefficients of V/K and
mV at room temperature, respectively. The resulting power factor of Co/Cu
nanowire networks at room temperature ( mW/Km) is larger than
those of state of the art thermoelectric materials, such as BiTe alloys and the
magneto-power factor ratio reaches about 100\% over a wide temperature range.
Validation of magnetic control of heat flow achieved by taking advantage of the
spin-dependent thermoelectric properties of flexible macroscopic nanowire
networks lay the groundwork to design shapeable thermoelectric coolers
exploiting the spin degree of freedom.Comment: 11 pages, 7 figure
Self consistent measurement and removal of the dipolar interaction field in magnetic particle assemblies and the determination of their intrinsic switching field distribution
"Using low density arrays of bistable magnetic nanowires as a model dipolar system, it is shown that the dipolar interaction field coefficient can be measured from the remanence curves as well as from other functions of the isothermal remanent magnetization and the DC demagnetization remanence obtained as an affine transformation of the Wohlfarth relation. Based on mean field arguments, these measurements are used to subtract and remove the contribution of the configuration dependent dipolar interaction field from the major loop and remanence curves. The corrected remanence curves are first used to obtain the intrinsic switching field distribution of the nanowire array and then to validate this approach showing that they yield results consistent with the Wohlfarth relation for an assembly of noninteracting particles, thus providing a self-consistent procedure to verify the measured values of the interaction field and its removal from the measurements.
Memristive and tunneling effects in 3D interconnected silver nanowires
Due to their memristive properties nanowire networks are very promising for
neuromorphic computing applications. Indeed, the resistance of such systems can
evolve with the input voltage or current as it confers a synaptic behaviour to
the device. Here, we propose a network of silver nanowires (Ag-NWs) which are
grown in a nanopourous membrane with interconnected nanopores by
electrodeposition. This bottom-up approach fabrication method gives a
conducting network with a 3D architecture and a high density of Ag-NWs. The
resulting 3D interconnected Ag-NW network exhibits a high initial resistance as
well as a memristive behavior. It is expected to arise from the creation and
the destruction of conducting silver filaments inside the Ag-NW network.
Moreover, after several cycles of measurement, the resistance of the network
switches from a high resistance regime, in the GOhm range, with a tunnel
conduction to a low resistance regime, in the kOhm range.Comment: 8 pages, 5 figure
Weak localization and coulomb interaction in graphite intercalation compounds and related materials
The effects of weak-localization and electron-electron interaction have to be invoked to explain anomalies in the resistivity and the magnetoresistance of quasi two-dimensional electron systems formed in acceptor graphite intercalation compounds and in pregraphitic carbon materials. After introducing the basic concepts involved in the physics of these phenomena, a review is given of recent data for the low temperature electronic transport properties in these materials.Anglai
Magnetic Nanowires
Magnetic nanowires are attractive materials because of their morphology-dependent remarkable properties suitable for various advanced technologies in sensing, data storage, spintronics, biomedicine and microwave devices, etc. The recent advances in synthetic strategies and approaches for the fabrication of complex structures, such as parallel arrays and 3D networks of one-dimensional nanostructures, including nanowires, nanotubes, and multilayers, are presented. The simple template-assisted electrodeposition method enables the fabrication of different nanowire-based architectures with excellent control over geometrical features, morphology and chemical composition, leading to tunable magnetic, magneto-transport and thermoelectric properties. This review article summarizing the work carried out at UCLouvain focuses on the magnetic and spin-dependent transport properties linked to the material and geometrical characteristics
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