Current-Induced Excitations in Single Cobalt Ferromagnetic Layer Nanopillars

Özyilmaz, Barbaros; Kent, Andrew D.; Sun, J. Z.; Rooks, M. J.; Koch, R. H.

doi:10.1103/physrevlett.93.176604

Cited by 82 publications

(91 citation statements)

References 14 publications

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“…The former are in good agreement with previous theoretical [27,39] and experimental studies [36]. They provide an improved understanding of the coupled dynamics between magnetizations and spin transport, and the excitation of spin wave modes for negative lateral spin transfer torques.…”

Section: Discussionsupporting

confidence: 79%

“…[27], several experimental [36][37][38] and theoretical [28,[39][40][41] studies have been performed to understand the lateral spin diffusion effect. Özyilmaz et al [36] experimentally observed current-induced excitation of a single ferromagnetic layer. For an asymmetric Cu/Co/Cu nanopillar structure, current-induced excitations were observed for only one polarity of the current, where, according to the prediction [27], the lateral spin transfer torque should increase the magnetization inhomogeneity.…”

Section: Previous Studies On Non-local Spin Transfer Torque Due To Lamentioning

confidence: 99%

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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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Section: Discussionsupporting

confidence: 79%

Section: Previous Studies On Non-local Spin Transfer Torque Due To Lamentioning

confidence: 99%

Self-consistent calculation of spin transport and magnetization dynamics

et al. 2013

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“…Both the threshold currents and the current induced hysteresis in these junctions exhibit a well defined magnetic field dependence. Similar to the high field excitations, 18 the low field single layer switching events lead to a low resistance state. However, the threshold currents and the corresponding changes in device resistance in the two regimes are very distinct.…”

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confidence: 99%

“…With a few exceptions 17,18 spin transfer devices consist of at least two exchange decoupled ferromagnetic regions, which play distinct roles. One of these regions is designed such that it simultaneously provides both a spin polarized current and acts as a reference layer relative to which the manipulation of the second ferromagnetic region is detected with the giant magnetoresistance effect (GMR).…”

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confidence: 99%

Current-induced switching in single ferromagenetic layer nanopillar junctions

Özyilmaz

Kent

2006

Applied Physics Letters

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Current induced magnetization dynamics in asymmetric Cu/Co/Cu single magnetic layer nanopillars has been studied experimentally at room temperature and in low magnetic fields applied perpendicular to the thin film plane. In sub-100 nm junctions produced using a nanostencil process a bistable state with two distinct resistance values is observed. Current sweeps at fixed applied fields reveal hysteretic and abrupt transitions between these two resistance states. The current induced resistance change is 0.5%, a factor of 5 greater than the anisotropic magnetoresistance (AMR) effect. We present an experimentally obtained low field phase diagram of current induced magnetization dynamics in single ferromagnetic layer pillar junctions. 75.60.Jk, 75.30.Ds, 75.75.1a

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“…Owing to its non-conservative nature, this spin torque (ST) can act as effective negative magnetic damping and thereby excite magnetization selfoscillations 3,4 . ST oscillators (STO) have been realized in nanoscale spin valves 3,[5][6][7] , point contacts to magnetic multilayers [8][9][10] and nanoscale magnetic tunnel junctions [11][12][13][14][15] . Recently, a new type of STO based on current-induced spin orbit (SO) torques in a Permalloy(Py)/platinum(Pt) bilayer was demonstrated [16][17][18] .…”

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confidence: 99%

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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Current-Induced Excitations in Single Cobalt Ferromagnetic Layer Nanopillars

Cited by 82 publications

References 14 publications

Self-consistent calculation of spin transport and magnetization dynamics

Self-consistent calculation of spin transport and magnetization dynamics

Current-induced switching in single ferromagenetic layer nanopillar junctions

Nanowire spin torque oscillator driven by spin orbit torques

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