Measurement of the spin-transfer-torque vector in magnetic tunnel junctions

Sankey, J. C.; Cui, Yong‐Tao; Sun, J. Z.; Slonczewski, J. C.; Buhrman, R. A.; Ralph, Daniel

doi:10.1038/nphys783

Cited by 607 publications

(554 citation statements)

References 27 publications

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“…Since STT is currently the most promising method for magnetization switching in MRAMs, the bias behavior of STT in MTJs with passive barriers has been the subject of intensive research both experimentally [37][38][39] and theoretically [40][41][42][43][44][45][46] . However, exploiting the ferroelectric polarization switching to control the STT components in non-collinear MFTJs has not been investigated.…”

Section: Introductionmentioning

confidence: 99%

Ferroelectric control of spin-transfer torque in multiferroic tunnel junctions

et al. 2015

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Based on model calculations we predict electric-field control of the spin transfer torque (STT) in magnetic tunnel junctions with ferroelectric barriers. We demonstrate that the bias dependence of the in-plane, T , and out-of-plane, T ⊥ , components of the STT can be dramatically modified by the ferroelectric polarization. In particular, the magnitude of the STT can be enhanced or suppressed by switching the polarization direction and in some cases the sign of STT can be toggled. The underlying mechanism is the combination of polarization-induced symmetry breaking and the interplay of the bias-induced and polarization-induced spin-dependent screening giving rise to a rich behavior of the electrostatic potential energy profile. These properties could lead to enhanced switching efficiency in STT-based devices and open a new avenue for applications of multiferroic devices.

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Section: Introductionmentioning

confidence: 99%

Ferroelectric control of spin-transfer torque in multiferroic tunnel junctions

et al. 2015

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“…The spin-torque diode effect enables quantitative measurements of STT parameters. [7][8][9] In this work, we use the spin-torque diode effect to investigate the dependence of in-plane and perpendicular spin torques on MgO tunnel barrier thickness. The tunnel barrier determines the transport properties of the device, as it affects the tunneling magnetoresistance (TMR) ratio, the resistance area (RA) product, and the coupling between the FL and the reference layer (RL).…”

Section: Introductionmentioning

confidence: 99%

Influence of MgO tunnel barrier thickness on spin-transfer ferromagnetic resonance and torque in magnetic tunnel junctions

et al. 2013

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Spin-transfer ferromagnetic resonance (ST-FMR) in symmetric magnetic tunnel junctions (MTJs) with a varied thickness of the MgO tunnel barrier (0.75 nm < tMgO < 1.05 nm) is studied using the spin-torque diode effect. The application of an RF current into nanosized MTJs generates a DC mixing voltage across the device when the frequency is in resonance with the resistance oscillations arising from the spin transfer torque. Magnetization precession in the free and reference layers of the MTJs is analyzed by comparing ST-FMR signals with macrospin and micromagnetic simulations. From ST-FMR spectra at different DC bias voltage, the in-plane and perpendicular torkances are derived. The experiments and free-electron model calculations show that the absolute torque values are independent of tunnel barrier thickness. The influence of coupling between the free and reference layer of the MTJs on the ST-FMR signals and the derived torkances are discussed.

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“…Generally, the mixing conductance has a real and an imaginary part, which couple to the in-plane and out-of-plane terms in the dynamics respectively. Although the outof-plane spin transfer torque is important in magnetic tunnel junctions [45][46][47][48][49][50][51][52][53], it is negligible in fully metallic multilayers [54,55]. Thus we neglect Im(G  ) and the associated out-of-plane spin transfer torque.…”

Section: Modeling Schemementioning

confidence: 99%

Self-consistent calculation of spin transport and magnetization dynamics

et al. 2013

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A spin-polarized current transfers its spin-angular momentum to a local magnetization, exciting various types of current-induced magnetization dynamics. So far, most studies in this field have focused on the direct effect of spin transport on magnetization dynamics, but ignored the feedback from the magnetization dynamics to the spin transport and back to the magnetization dynamics. Although the feedback is usually weak, there are situations when it can play an important role in the dynamics. In such situations, simultaneous, self-consistent calculations of the magnetization dynamics and the spin transport can accurately describe the feedback. This review describes in detail the feedback mechanisms, and presents recent progress in self-consistent calculations of the coupled dynamics. We pay special attention to three representative examples, where the feedback generates non-local effective interactions for the magnetization after the spin accumulation has been integrated out. Possibly the most dramatic feedback example is the dynamic instability in magnetic nanopillars with a single magnetic layer. This instability does not occur without non-local feedback. We demonstrate that full self-consistent calculations generate simulation results in much better agreement with experiments than previous calculations that addressed the feedback effect approximately.The next example is for more typical spin valve nanopillars. Although the effect of feedback is less dramatic because even without feedback the current can make stationary states unstable and induce magnetization oscillation, the feedback can still have important consequences. For instance, we show that the feedback can reduce the linewidth of oscillations, in agreement with experimental observations. A key aspect of this reduction is the suppression of the excitation of short wave length spin waves by the non-local feedback.Finally, we consider nonadiabatic electron transport in narrow domain walls. The non-local feedback in these systems leads to a significant renormalization of the effective nonadiabatic 3 spin transfer torque. These examples show that the self-consistent treatment of spin transport and magnetization dynamics is important for understanding the physics of the coupled dynamics and for providing a bridge between the ongoing research fields of current-induced magnetization dynamics and the newly emerging fields of magnetization-dynamics-induced generation of charge and spin currents.

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Measurement of the spin-transfer-torque vector in magnetic tunnel junctions

Cited by 607 publications

References 27 publications

Ferroelectric control of spin-transfer torque in multiferroic tunnel junctions

Ferroelectric control of spin-transfer torque in multiferroic tunnel junctions

Influence of MgO tunnel barrier thickness on spin-transfer ferromagnetic resonance and torque in magnetic tunnel junctions

Self-consistent calculation of spin transport and magnetization dynamics

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