Bennett clocking of nanomagnetic logic using multiferroic single-domain nanomagnets

Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

doi:10.1063/1.3506690

Cited by 131 publications

(121 citation statements)

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“…Popular approaches include passing a spin current through the soft layer to generate a spin transfer torque 2-7 or spin orbit torque [8][9][10][11] or domain wall motion [12][13] . Other approaches involve using voltage controlled magnetic anisotropy 14 , magnetoelectric effects 15-17 , magnetoionic effects 18 and magnetoelastic effects [19][20][21][22][23][24][25] . Unfortunately, generation of a spin current requires passing a charge current through a resistor that dissipates excessive energy, making the spin-current based schemes relatively energy-inefficient 26,27 .…”

mentioning

confidence: 99%

“…One magnetoelastic scheme, the so-called "straintronic" switching, involves rotating the magnetization of a magnetostrictive soft layer with mechanical strain generated by applying a voltage across an underlying piezoelectric layer with a suitable arrangement of electrodes [28][29][30] . The voltage generates strain in the piezoelectric, which is partially or completely transferred to the elliptical magnetostrictive soft layer,and rotates magnetization by the Villari effect [19][20][21][22][23][24][25] . It has been predicted theoretically that large angle (~90 o ) rotation in ~100 nm feature sized nanomagnets made of highly magnetostrictive materials (Terfenol-D, FeGa) will dissipate only ~1 aJ of energy to occur in ~1 ns [31][32][33] .…”

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Experimental Demonstration of Complete 180° Reversal of Magnetization in Isolated Co Nanomagnets on a PMN–PT Substrate with Voltage Generated Strain

et al. 2017

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Rotating the magnetization of a shape anisotropic magnetostrictive nanomagnet with voltagegenerated stress/strain dissipates much less energy than most other magnetization rotation schemes, but its application to writing bits in non-volatile magnetic memory has been hindered by the fundamental inability of stress/strain to rotate magnetization by full 180 o . Normally, stress/strain can rotate the magnetization of a shape anisotropic elliptical nanomagnet by only up to 90 o , resulting in incomplete magnetization reversal. Recently, we predicted that applying uniaxial stress sequentially along two different axes that are not collinear with the major or minor axis of the elliptical nanomagnet will rotate the magnetization by full 180 o [1]. Here, we demonstrate this complete 180 o rotation in elliptical Co-nanomagnets (fabricated on a piezoelectric substrate) at room temperature. The two stresses are generated by sequentially applying voltages to two pairs of shorted electrodes placed on the substrate such that the line joining the centers of the electrodes in one pair intersects the major axis of a nanomagnet at ~+30 o and the line joining the centers of the electrodes in the other pair intersects at ~ -30 o . A finite element analysis has been performed to determine the stress distribution underneath the nanomagnets when one or both pairs of electrodes are activated, and this has been approximately incorporated into a micromagnetic simulation of magnetization dynamics to confirm that the generated stress can produce the observed magnetization rotations. This result portends an extremely energy-efficient non-volatile "straintronic" memory technology predicated on writing bits in nanomagnets with electrically generated stress.Nanomagnets are the bedrock of non-volatile memory. A magnetic random access memory (MRAM) cell is implemented with a magneto-tunneling junction (MTJ) consisting of two nanomagnetic layers, one hard and one soft, separated by a spacer (tunneling) layer. The soft layer is often shaped like an elliptical disc which, if sufficiently thick, has two in-plane stable magnetization directions pointing in opposite directions along the major axis of the ellipse. They encode and store the binary bits 0 and 1. The stored bit * Corresponding author. E-mail: sbandy@vcu.edu is "read" by measuring the resistance of the MTJ which has two discrete values depending on the two magnetization orientations of the soft layer, i.e., for the two bits 0 and 1. "Writing" of bits is accomplished by switching the magnetization of the soft layer between the two anti-parallel directions of stable magnetization (180 0 rotation of the magnetization) with an external agent.There are many strategies to rotate the magnetization of the soft layer. Popular approaches include passing a spin current through the soft layer to generate a spin transfer torque 2-7 or spin orbit torque [8][9][10][11] or domain wall motion [12][13] . Other approaches involve using voltage controlled magnetic anisotropy 14 , magnetoelectric effects 15-17 ...

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confidence: 99%

Experimental Demonstration of Complete 180° Reversal of Magnetization in Isolated Co Nanomagnets on a PMN–PT Substrate with Voltage Generated Strain

et al. 2017

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“…This strain/stress can cause the magnetization of the magnetostrictive layer to rotate by a large angle [16], which has been demonstrated in recent experiments, although not at the nanoscale [17]. These rotations are sufficiently large to fulfill the requirements of Bennett clocking in logic chains [13]. In the specific configuration discussed in this paper, the voltage strains the piezoelectric layer via the d 31 coupling…”

Section: Introductionmentioning

confidence: 66%

“…Recently, we showed that local clocking of NML can be implemented by applying a small voltage to a nanomagnet made of multiferroics [13]. Such a nanomagnet consists of two elastically coupled piezoelectric and magnetostrictive layers as shown in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

“…The same could have been achieved by applying the electric field along the y-direction direction, which will generate a stress along it via the d 33 coupling/ In ref. [13], we considered Bennett clocking of logic chains where the logic switches are ellipsoidal multiferroic nanomagnets of major axis = 105 nm and minor axis = 95 nm. Each multiferroic nanomagnet is composed of 10 nm thick Ni (magnetostrictive) layer and 40 nm thick lead zirconium titanate, or PZT, (piezoelectric) layer that are elastically coupled.…”

Section: Introductionmentioning

confidence: 99%

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Magnetization dynamics, Bennett clocking and associated energy dissipation in multiferroic logic

Fashami¹,

Roy²,

Atulasimha³

et al. 2011

Nanotechnology

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It has been recently shown that the magnetization of a multiferroic nanomagnet, consisting of a magnetostrictive layer elastically coupled to a piezoelectric layer, can be rotated by a large angle if a tiny voltage of few tens of mV is applied to the piezoelectric layer. The potential generates stress in the magnetostrictive layer and rotates its magnetization by ~ 90 0 to implement Bennett clocking in nanomagnetic logic chains. Because of the small voltage needed, this clocking method is far more energy-efficient than those that would employ spin transfer torque or magnetic fields to rotate the magnetization. In order to assess if such a clocking scheme can be also reasonably fast, we have studied the magnetization dynamics of a multiferroic logic chain with nearest neighbor dipole coupling using the Landau-Lifshitz-Gilbert (LLG) equation. We find that clock rates of ~ 2 GHz are feasible while still maintaining the exceptionally high energy-efficiency. For this clock rate, the energy dissipated per clock cycle per bit flip is ~52,000 kT at room temperature in the clocking circuit for properly designed nanomagnets. Had we used spin transfer torque to clock at the same rate, the

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Hybrid Spintronics‐Strainronics

Biswas

D'Souza

Bandyopadhyay

et al. 2016

Nanomagnetic and Spintronic Devices for Energy‐Efficient Memory and Computing

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Bennett clocking of nanomagnetic logic using multiferroic single-domain nanomagnets

Cited by 131 publications

References 18 publications

Experimental Demonstration of Complete 180° Reversal of Magnetization in Isolated Co Nanomagnets on a PMN–PT Substrate with Voltage Generated Strain

Experimental Demonstration of Complete 180° Reversal of Magnetization in Isolated Co Nanomagnets on a PMN–PT Substrate with Voltage Generated Strain

Magnetization dynamics, Bennett clocking and associated energy dissipation in multiferroic logic

Hybrid Spintronics‐Strainronics

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