84 research outputs found
A ferroelectric memristor
Memristors are continuously tunable resistors that emulate synapses.
Conceptualized in the 1970s, they traditionally operate by voltage-induced
displacements of matter, but the mechanism remains controversial. Purely
electronic memristors have recently emerged based on well-established physical
phenomena with albeit modest resistance changes. Here we demonstrate that
voltage-controlled domain configurations in ferroelectric tunnel barriers yield
memristive behaviour with resistance variations exceeding two orders of
magnitude and a 10 ns operation speed. Using models of ferroelectric-domain
nucleation and growth we explain the quasi-continuous resistance variations and
derive a simple analytical expression for the memristive effect. Our results
suggest new opportunities for ferroelectrics as the hardware basis of future
neuromorphic computational architectures
Vertical current induced domain wall motion in MgO-based magnetic tunnel junction with low current densities
Shifting electrically a magnetic domain wall (DW) by the spin transfer
mechanism is one of the future ways foreseen for the switching of spintronic
memories or registers. The classical geometries where the current is injected
in the plane of the magnetic layers suffer from a poor efficiency of the
intrinsic torques acting on the DWs. A way to circumvent this problem is to use
vertical current injection. In that case, theoretical calculations attribute
the microscopic origin of DW displacements to the out-of-plane (field-like)
spin transfer torque. Here we report experiments in which we controllably
displace a DW in the planar electrode of a magnetic tunnel junction by vertical
current injection. Our measurements confirm the major role of the out-of-plane
spin torque for DW motion, and allow to quantify this term precisely. The
involved current densities are about 100 times smaller than the one commonly
observed with in-plane currents. Step by step resistance switching of the
magnetic tunnel junction opens a new way for the realization of spintronic
memristive devices
Spin torque resonant vortex core expulsion for an efficient radio-frequency detection scheme
Spin-polarised radio-frequency currents, whose frequency is equal to that of
the gyrotropic mode, will cause an excitation of the core of a magnetic vortex
confined in a magnetic tunnel junction. When the excitation radius of the
vortex core is greater than that of the junction radius, vortex core expulsion
is observed, leading to a large change in resistance, as the layer enters a
predominantly uniform magnetisation state. Unlike the conventional spin-torque
diode effect, this highly tunable resonant effect will generate a voltage which
does not decrease as a function of rf power, and has the potential to form the
basis of a new generation of tunable nanoscale radio-frequency detectors
Giant Electroresistance in Edge Metal-Insulator-Metal Tunnel Junctions Induced by Ferroelectric Fringe Fields
An enormous amount of research activities has been devoted to developing new types of non-volatile memory devices as the potential replacements of current flash memory devices. Theoretical device modeling was performed to demonstrate that a huge change of tunnel resistance in an Edge Metal-Insulator-Metal (EMIM) junction of metal crossbar structure can be induced by the modulation of electric fringe field, associated with the polarization reversal of an underlying ferroelectric layer. It is demonstrated that single three-terminal EMIM/Ferroelectric structure could form an active memory cell without any additional selection devices. This new structure can open up a way of fabricating all-thin-film-based, high-density, high-speed, and low-power non-volatile memory devices that are stackable to realize 3D memory architectureope
Magnetic domain wall motion by spin transfer
The discovery that a spin polarized current can exert a large torque on a
ferromagnet through a transfusion of spin angular momentum, offers a new way to
control a magnetization by simple current injection, without the help of an
applied external field. Spin transfer can be used to induce magnetization
reversals and oscillations, or to control the position of a magnetic domain
wall. In this review, we focus on this last mechanism, which is today the
subject of an extensive research, both because the microscopic details for its
origin are still debated, but also because promising applications are at stake
for non-volatile magnetic memories
Overview of emerging memristor families from resistive memristor to spintronic memristor
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