Control of Magnetic Fluctuations by Spin Current

Demidov, V. E.; Urazhdin, Sergei; Edwards, Eric R. J.; Stiles, Mark D.; McMichael, Robert D.; Demokritov, S. O.

doi:10.1103/physrevlett.107.107204

Cited by 166 publications

(163 citation statements)

References 29 publications

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“…Recent experiments 33 demonstrated that application of spatially uniform SO torques to an extended ferromagnetic film does not result in excitation of magnetic self-oscillations because the amplitudes of all spin wave modes of the film are limited by nonlinear magnon scattering processes. Therefore, our observation of self-oscillatory dynamics excited by SO torques in the entire 1.8 mm long active region of a ferromagnetic nanowire is surprising.…”

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

“…A recent study 33 of spatially uniform ST applied to an extended ferromagnetic film revealed that coherent self-oscillations of magnetization cannot be excited in this two-dimensional (2D) magnetic system. Instead, ST was shown to significantly reduce the saturation magnetization of the film 33 . The absence of ST-driven self-oscillations in a 2D ferromagnet was attributed to amplitude-dependent damping arising from nonlinear magnon scattering that prevents any of the multiple interacting spin wave modes of the system from reaching the state of large-amplitude self-oscillations.…”

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confidence: 99%

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Nanowire spin torque oscillator driven by spin orbit torques

et al. 2014

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Spin torque from spin current applied to a nanoscale region of a ferromagnet can act as negative magnetic damping and thereby excite self-oscillations of its magnetization. In contrast, spin torque uniformly applied to the magnetization of an extended ferromagnetic film does not generate self-oscillatory magnetic dynamics but leads to reduction of the saturation magnetization. Here we report studies of the effect of spin torque on a system of intermediate dimensionality-a ferromagnetic nanowire. We observe coherent self-oscillations of magnetization in a ferromagnetic nanowire serving as the active region of a spin torque oscillator driven by spin orbit torques. Our work demonstrates that magnetization selfoscillations can be excited in a one-dimensional magnetic system and that dimensions of the active region of spin torque oscillators can be extended beyond the nanometre length scale.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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Nanowire spin torque oscillator driven by spin orbit torques

et al. 2014

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“…This reversed domain wall motion with high speed cannot be explained by conventional adiabatic and nonadiabatic spin transfer torques, but may be explained by a damping-like spin transfer torque in addition to all other spin transfer torques (i.e., adiabatic, nonadiabatic, and the field-like torques) [156] and the Dzyaloshinskii-Moriya interaction [159]. The damping-like spin transfer torque may originate from a spin Hall effect in a heavy metal layer like Pt [159][160][161][162][163][164][165] and/or a nonadiabatic correction to the field-like torque [155][156][157][158]. This damping-like torque also allows switching the magnetization by in-plane currents [149,164,166].…”

Section: Discussionmentioning

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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“…As it has been seen that spin-transfer torques can redistribute energy across fluctuation modes in a nanomagnet [34,35], competing fluctuation modes could be the origin of a distribution of switching pathways. We begin with a Gaussian distribution of switching rates i , each with their own energy barrier ξ i .…”

Section: Testing the Model: Switching Field Distributions Under Cmentioning

confidence: 99%

Switching field distributions with spin transfer torques in perpendicularly magnetized spin-valve nanopillars

et al. 2014

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We present switching field distributions of spin-transfer-assisted magnetization reversal in perpendicularly magnetized Co/Ni multilayer spin-valve nanopillars at room temperature. Switching field measurements of the Co/Ni free layer of spin-valve nanopillars with a 50 nm × 300 nm ellipse cross section were conducted as a function of current. The validity of a model that assumes a spin-current-dependent effective barrier for thermally activated reversal is tested by measuring switching field distributions under applied direct currents. We show that the switching field distributions deviate significantly from the double exponential shape predicted by the effective barrier model, beginning at applied currents as low as half of the zero field critical current. Barrier heights extracted from switching field distributions for currents below this threshold are a monotonic function of the current. However, the thermally induced switching model breaks down for currents exceeding the critical threshold.

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Control of Magnetic Fluctuations by Spin Current

Cited by 166 publications

References 29 publications

Nanowire spin torque oscillator driven by spin orbit torques

Nanowire spin torque oscillator driven by spin orbit torques

Self-consistent calculation of spin transport and magnetization dynamics

Switching field distributions with spin transfer torques in perpendicularly magnetized spin-valve nanopillars

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