Programmable computing with a single magnetoresistive element

Ney, A.; Pampuch, C.; Koch, R.; Ploog, K.

doi:10.1038/nature02014

Cited by 379 publications

(269 citation statements)

References 11 publications

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“…It has been suggested [8,9] that MRAM-type cells with very large ratios of parallel to anti-parallel conductance might enable a new type of computer architecture in which logic circuits are reprogrammed dynamically. Such a device would be similar to a field programmable gate array that could be reprogrammed on a nanosecond timescale.…”

Section: Other Applicationsmentioning

confidence: 99%

Tunneling magnetoresistance from a symmetry filtering effect

Butler

2008

Science and Technology of Advanced Materials

138

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Section: Other Applicationsmentioning

confidence: 99%

Tunneling magnetoresistance from a symmetry filtering effect

Butler

2008

Science and Technology of Advanced Materials

138

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“…TMR effect presents an excellent opportunity for spintronics, it is the key to magnetoresistive random-access-memory [5], programmable logic elements [6], and magnetic sensors. The high TMR values in MgO based MTJs have generated great excitement for practical applications.…”

mentioning

confidence: 99%

First Principles Modeling of Tunnel Magnetoresistance ofFe/MgO/FeTrilayers

et al. 2006

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By carrying out density functional theory analysis within the Keldysh non-equilibrium Green's functional formalism, we have calculated the nonlinear and non-equilibrium quantum transport properties of Fe/MgO/Fe trilayer structures as a function of external bias voltage. For well relaxed atomic structures of the trilayer, the equilibrium tunnel magnetoresistance ratio (TMR) is found to be very large and also fairly stable against small variations in the atomic structure. As a function of external bias voltage, the TMR reduces monotonically to zero with a voltage scale of about 1V, in agreement with experimental observations. We present understanding of the nonequilibrium transport properties by investigating microscopic details of the scattering states and the Bloch bands of the Fe leads.PACS numbers: 85.35.-p, 72.25.-b, 85.65.+h Since the prediction and elegant physics explanation [1,2] that magnetic tunnel junction (MTJ) of Fe/MgO/Fe trilayer structure may have very high tunnel magnetoresistance (TMR), MgO based MTJ has progressed at a rapid pace in recent years and produced the highest measured TMR at room temperature: several groups [3,4] reported TMR ratio in the range of 180% to 250%. TMR effect presents an excellent opportunity for spintronics, it is the key to magnetoresistive random-access-memory . There are, however, a number of important issues remain to be understood from atomic first principles. Most existing work predicted[1, 2] TMR to be greater than 1000%, experimental data are still lower. More seriously is that experimental data on MgO based MTJs show a monotonically decreasing TMR as a function of applied bias voltage [3,4] and it reduces to zero when bias is about one volt. To the best of our knowledge, there have been two atomistic calculations of bias dependence of TMR for MgO barriers [7,8], both used the Korringa-Kohn-Rostoker numerical technique. Ref.7 predicted a substantial increase of TMR versus bias for the asymmetric system analyzed there, while Ref.8 found a roughly constant TMR, a decaying TMR, or an entirely negative TMR versus bias depending on atomic structures of the interface. The origin of these differences were not clear. Earlier theory[9] on Al 2 O 3 based MTJs has attributed small bias dependence of magneto-resistance to magnon scattering. Given the extreme importance of MgO based MTJ in near future spintronics and the accumulated experimental data, further quantitative understanding on quantum transport in Fe/MgO/Fe at finite bias is urgently needed.Here we present a first principles atomistic analysis of nonlinear and non-equilibrium quantum transport in Fe/MgO/Fe MTJ. We use a state-of-the-art quantum transport technique [10,11] which is based on real-space, Keldysh nonequilibrium Green's function (NEGF) formalism combined with density functional theory (DFT). The basic idea of the NEGF-DFT formalism [10] is to calculate device Hamiltonian and electronic structure by DFT, populate this electronic structure using NEGF which properly takes into account nonequilibrium q...

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“…The traditional method of switching nanomagnets is to generate a local magnetic field in the vicinity of a magnet with a current [63,66]. The current flows in a loop circling the magnet.…”

Section: Switching a Nanomagnet: Penny-wise And Pound-foolishmentioning

confidence: 99%

Information Processing with Electron Spins

Bandyopadhyay

2012

ISRN Materials Science

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Information processors process information in a variety of ways. The human brain processes information through a highly interconnected system of neurons and synapses, while a digital computer processes information by having a binary switch toggle on and off in response to a stream of binary bits. The "switch" is the most primitive unit of the modern computer. The better it is (faster, more energy efficient, more reliable, etc.), the more advanced is the computer hardware. Energy efficiency, however, is more important than any other attribute, not so much because energy is costly, but because too much energy dissipation prevents increasing the density of switches on a chip that is necessary to make the chip increasingly more powerful. Reducing dissipation entails radically new and often revolutionary approaches for implementing the switch. One such approach is to encode digital bit information in the spin polarization of a single electron (or ensemble of electrons) and then using two mutually antiparallel polarizations to represent the binary bits 0 and 1. Switching between the bits can be accomplished by simply flipping the polarizations of the spins, which takes very little energy. Such switches are extremely energy efficient if designed properly, but they are somewhat slower than traditional transistor-based switches and can be more error prone. This paper discusses the pros and cons of spin-based switches and introduces the reader to the most recent advancements in information processing predicated on encoding information in electron spin polarization.

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Programmable computing with a single magnetoresistive element

Cited by 379 publications

References 11 publications

Tunneling magnetoresistance from a symmetry filtering effect

Tunneling magnetoresistance from a symmetry filtering effect

First Principles Modeling of Tunnel Magnetoresistance ofFe/MgO/FeTrilayers

Information Processing with Electron Spins

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