144 research outputs found
Multi-state and non-volatile control of graphene conductivity with surface electric fields
Planar electrodes patterned on a ferroelectric substrate are shown to provide
lateral control of the conductive state of a two-terminal graphene stripe. A
multi-level and on-demand memory control of the graphene resistance state is
demonstrated under low sub-coercive electric fields, with a susceptibility
exceeding by more than two orders of magnitude those reported in a vertical
gating geometry. Our example of reversible and low-power lateral control over
11 memory states in the graphene conductivity illustrates the possibility of
multimemory and multifunctional applications, as top and bottom inputs remain
accessible.Comment: Graphene ferroelectric lateral structure for multi-state and
non-volatile conductivity control, 4 pages, 4 figure
Voltage-controlled inversion of tunnel magnetoresistance in epitaxial Nickel/Graphene/MgO/Cobalt junctions
We report on the fabrication and characterization of vertical spin-valve
structures using a thick epitaxial MgO barrier as spacer layer and a
graphene-passivated Ni film as bottom ferromagnetic electrode. The devices show
robust and scalable tunnel magnetoresistance, with several changes of sign upon
varying the applied bias voltage. These findings are explained by a model of
phonon-assisted transport mechanisms that relies on the peculiarity of the band
structure and spin density of states at the hybrid graphene|Ni interface
Electrical Writing of Magnetic and Resistive Multistates in CoFe Films Deposited onto Pb[ZrTi]O
Electric control of magnetic properties is an important challenge for modern
magnetism and spintronic development. In particular, an ability to write
magnetic state electrically would be highly beneficial. Among other methods,
the use of electric field induced deformation of piezoelectric elements is a
promising low-energy approach for magnetization control. We investigate the
system of piezoelectric substrate Pb[ZrTi]O with CoFe
overlayers, extending the known reversible bistable electro-magnetic coupling
to surface and multistate operations, adding the initial state reset
possibility. Increasing the CoFe thickness improves the magnetoresistive
sensitivity, but at the expenses of decreasing the strain-mediated coupling,
with optimum magnetic thin film thickness of the order of 100 nm. The simplest
resistance strain gauge structure is realized and discussed as a multistate
memory cell demonstrating both resistive memory (RRAM) and magnetoresistive
memory (MRAM) functionalities in a single structure.Comment: 20th International Conference on Magnetism, ICM 2015, 11 pages, 7
figure
Light controlled magnetoresistance and magnetic field controlled photoresistance in CoFe film deposited on BiFeO3
We present a magnetoresistive-photoresistive device based on the interaction
of a piezomagnetic CoFe thin film with a photostrictive BiFeO3 substrate that
undergoes light-induced strain. The magnitude of the resistance and
magnetoresistance in the CoFe film can be controlled by the wavelength of the
incident light on the BiFeO3. Moreover, a light-induced decrease in anisotropic
magnetoresistance is detected due to an additional magnetoelastic contribution
to magnetic anisotropy of the CoFe film. This effect may find applications in
photo-sensing systems, wavelength detectors and can possibly open a research
development in light-controlled magnetic switching properties for next
generation magnetoresistive memory devices.Comment: 5 pages, 4 figures, journal pape
Subcoercive and multilevel ferroelastic remnant states with resistive readout
Ferroelectric devices use their electric polarization ferroic order as the
switching and storage physical quantity for memory applications. However,
additional built-in physical quantities and memory paradigms are requested for
applications. We propose here to take advantage of the multiferroic properties
of ferroelectrics, using ferroelasticity to create a remnant strain, persisting
after stressing the material by converse piezoelectricity means. While large
electric fields are needed to switch the polarization, here writing occurs at
subcoercive much lower field values, which can efficiently imprint multiple
remnant strain states. A proof-of-principle device, with the simplest and
non-optimized resistance strain detection design, is shown here to exhibit
13-memory states of high reproducibility and reliability. The related
advantages in lower power consumption and limited device fatigue make our
approach relevant for applications.Comment: Resistive random access memory-like (RRAM) effect is described.
Multistate non-volatile ferroelastic-resistive memor
The magnetoelectrochemical switch
In the field of spintronics, the archetype solid-state two-terminal device is the spin valve, where the resistance is controlled by the magnetization configuration. We show here how this concept of spin-dependent switch can be extended to magnetic electrodes in solution, by magnetic control of their chemical environment. Appropriate nanoscale design allows a huge enhancement of the magnetic force field experienced by paramagnetic molecular species in solutions, which changes between repulsive and attractive on changing the electrodes' magnetic orientations. Specifically, the field gradient force created within a sub-100-nm-sized nanogap separating two magnetic electrodes can be reversed by changing the orientation of the electrodes' magnetization relative to the current flowing between the electrodes. This can result in a breaking or making of an electric nanocontact, with a change of resistance by a factor of up to 103. The results reveal how an external field can impact chemical equilibrium in the vicinity of nanoscale magnetic circuits
Nanotrench for nano and microparticle electrical interconnects
We present a simple and versatile patterning procedure for the reliable and reproducible fabrication of high aspect ratio (10 4 ) electrical interconnects that have separation distances down to 20 nm and lengths of several hundreds of microns. The process uses standard optical lithography techniques and allows parallel processing of many junctions, making it easily scalable and industrially relevant. We demonstrate the suitability of these nanotrenches as electrical interconnects for addressing micro and nanoparticles by realizing several circuits with integrated species. Furthermore, low impedance metal-metal low contacts are shown to be obtained when trapping a single metal-coated microsphere in the gap, emphasizing the intrinsic good electrical conductivity of the interconnects, even though a wet process is used. Highly resistive magnetite-based nanoparticles networks also demonstrate the advantage of the high aspect ratio of the nanotrenches for providing access to electrical properties of highly resistive materials, with leakage current levels below 1 pA. © 2010 IOP Publishing Ltd
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