Electric-field-assisted switching in magnetic tunnel junctions

Wang, Wei Gang; Li, Mingen; Hageman, Stephen; Chien, C. L.

doi:10.1038/nmat3171

Cited by 927 publications

(755 citation statements)

References 38 publications

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“…Under the small perturbation limit, the second-order PHE voltage DV is linearly proportional to the current-induced magnetization reorientation Dm x as calculated in equation (2) and is therefore proportional to the transverse field including the SOF, in-plane Oersted field and calibration field h cal ,…”

Section: Current-induced Magnetization Reorientationmentioning

confidence: 99%

“…L ocal electrical manipulation of magnetization is a promising candidate for information storage and processing owing to the switching reliability and its easy large-scale integration [1][2][3][4] . One way to realize electrical control of magnetization is to leverage the spin-orbit interaction (SOI), through which an electric current exerts an effective field and torque on the magnetization 5,6 .…”

mentioning

confidence: 99%

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Quantifying interface and bulk contributions to spin–orbit torque in magnetic bilayers

et al. 2014

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Spin-orbit interaction-driven phenomena such as the spin Hall and Rashba effect in ferromagnetic/heavy metal bilayers enables efficient manipulation of the magnetization via electric current. However, the underlying mechanism for the spin-orbit interaction-driven phenomena remains unsettled. Here we develop a sensitive spin-orbit torque magnetometer based on the magneto-optic Kerr effect that measures the spin-orbit torque vectors for cobalt iron boron/platinum bilayers over a wide thickness range. We observe that the Slonczewskilike torque inversely scales with the ferromagnet thickness, and the field-like torque has a threshold effect that appears only when the ferromagnetic layer is thinner than 1 nm. Through a thickness-dependence study with an additional copper insertion layer at the interface, we conclude that the dominant mechanism for the spin-orbit interaction-driven phenomena in this system is the spin Hall effect. However, there is also a distinct interface contribution, which may be because of the Rashba effect.

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Section: Current-induced Magnetization Reorientationmentioning

confidence: 99%

mentioning

confidence: 99%

Quantifying interface and bulk contributions to spin–orbit torque in magnetic bilayers

et al. 2014

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“…13 Theoretically, the electric field effect on the MCA was investigated for various free-standing magnetic metal films 10,14-17 and Fe/MgO interfaces. 18,19 Very recently, electrically induced bistable magnetization switching was realized in MgO-based magnetic tunnel junctions at room temperature, 20,21 demonstrating the capabilities of this approach for magnetic data storage applications. 22 Alternatively, the interface magnetic anisotropy (and hence the magnetization orientation) may be tailored electronically by the ferroelectric polarization of an adjacent ferroelectric film.…”

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confidence: 97%

Ferroelectric Control of Magnetocrystalline Anisotropy at Cobalt/Poly(vinylidene fluoride) Interfaces

et al. 2012

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Electric field control of magnetization is one of the promising avenues for achieving high-density energy-efficient magnetic data storage. Ferroelectric materials can be especially useful for that purpose as a source of very large switchable electric fields when interfaced with a ferromagnet. Organic ferroelectrics, such as poly(vinylidene fluoride) (PVDF), have an additional advantage of being weakly bonded to the ferromagnet, thus minimizing undesirable effects such as interface chemical modification and/or strain coupling. In this work we use first-principles density functional calculations of Co/PVDF heterostructures to demonstrate the effect of ferroelectric polarization of PVDF on the interface magnetocrystalline anisotropy that controls the magnetization orientation. We show that switching of the polarization direction alters the magnetocrystalline anisotropy energy of the adjacent Co layer by about 50%, driven by the modification of the screening charge induced by ferroelectric polarization. The effect is reduced with Co oxidation at the interface due to quenching the interface magnetization. Our results provide a new insight into the mechanism of the magnetoelectric coupling at organic ferroelectric/ferromagnet interfaces and suggest ways to achieve the desired functionality in practice.

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“…Popular approaches include passing a spin current through the soft layer to generate a spin transfer torque [2][3][4][5][6][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][16][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%

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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Electric-field-assisted switching in magnetic tunnel junctions

Cited by 927 publications

References 38 publications

Quantifying interface and bulk contributions to spin–orbit torque in magnetic bilayers

Quantifying interface and bulk contributions to spin–orbit torque in magnetic bilayers

Ferroelectric Control of Magnetocrystalline Anisotropy at Cobalt/Poly(vinylidene fluoride) Interfaces

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

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