Phase-locking in double-point-contact spin-transfer devices

Mancoff, F. B.; Rizzo, Nicholas D.; Engel, Brad N.; Tehrani, S.

doi:10.1038/nature04036

Cited by 490 publications

(350 citation statements)

References 26 publications

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“…Practical applications of spin torque nano-oscillators (STNOs) require high output power levels and low phase noise 8,9,10 . Several approaches pursuing these goals, such as phase locking of arrays of STNOs 11,12,13,14 and development of STNOs based on magnetic tunnel junctions 15,16,17,18 are active areas of research.…”

Section: Introductionmentioning

confidence: 99%

“…The two-dimensional systems offer the advantage of phase locking of nearby STNOs via interaction by spin waves propagating in the common ferromagnetic free layer 11,12 . The phase locking regime is attractive from the practical point of view because the output power of STNOs increases and their phase noise decreases in this regime 11,12,13 .…”

Section: Introductionmentioning

confidence: 99%

“…Up to date, two major STNO geometries have been studied: (i) spin valve nanopillars in which propagation of magnetic excitations is restricted by the ferromagnet boundaries in all three spatial dimensions (zero-dimensional systems, 0D) 5,27,28 and (ii) point contacts to spin valves in which magnetic excitations can propagate in the plane of the spin valve (twodimensional systems, 2D) 6,8,11,12,29 . The two-dimensional systems offer the advantage of phase locking of nearby STNOs via interaction by spin waves propagating in the common ferromagnetic free layer 11,12 .…”

Section: Introductionmentioning

confidence: 99%

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Micromagnetic simulations of magnetization dynamics in a nanowire induced by a spin-polarized current injected via a point contact

Berkov

Boone

2011

Phys. Rev. B

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We present a detailed numerical analysis of the magnetization auto-oscillations induced in a thin NiFe nanowire by a direct spin polarized current injected via a square-shaped CoFe nanomagnet (a system experimentally studied in C. Boone et al., Phys. Rev. B 79, 140404 (2009)). We demonstrate that all auto-oscillation modes in the nanowire are localized under the nanocontact for magnetic field applied in the plane of the nanowire. This mode localization is induced by a strong stray magnetic field acting on the NiFe nanowire from the CoFe current injector. We find that the auto-oscillation frequency, power and the frequency shift with the current strongly depend on the exchange constant of NiFe. We also find that the auto-oscillation power depends non-monotonically on the CoFe saturation magnetization, and demonstrate that this effect has its origin in resonant excitation of the CoFe eigenmodes by magnetization oscillations in the NiFe nanowire. The calculated dependence of the oscillation frequency on current is in a good agreement with the experiment. However, the agreement between theory and experiment for the oscillation power is unsatisfactory. Finally, we have shown that an auto-oscillatory mode propagating along the nanowire in the system under study is possible when a sufficiently strong out-of-plane field is applied.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Micromagnetic simulations of magnetization dynamics in a nanowire induced by a spin-polarized current injected via a point contact

Berkov

Boone

2011

Phys. Rev. B

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“…Above all, the exciting topic in this research field is the synchronization of spin-torque oscillators by the magnetic [7][8][9][10] and/or electrical [11][12][13][14][15] couplings. The synchronization of spin-torque oscillators results in an enhancement of the emission power and an increase of the quality factor of the practical devices.…”

mentioning

confidence: 99%

Mutual synchronization of spin-torque oscillators consisting of perpendicularly magnetized free layers and in-plane magnetized pinned layers

Taniguchi

Tsunegi

2017

Appl. Phys. Express

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A mutual synchronization of spin-torque oscillators coupled through current injection is studied theoretically. Models of electrical coupling in parallel and series circuits are proposed. Solving the Landau-Lifshitz-Gilbert equation, excitation of in-phase or antiphase synchronization, depending on the ways the oscillators are connected, is found. It is also found from both analytical and numerical calculations that the current-frequency relations for both parallel and series circuits are the same as that for a single spin-torque oscillator.Spin-torque oscillators have been a fascinating research target in the field of spintronics from the viewpoints of both nonlinear science and practical applications such as microwave generator and communication devices [1][2][3][4][5][6]. Above all, the exciting topic in this research field is the synchronization of spin-torque oscillators by the magnetic [7][8][9][10] and/or electrical [11][12][13][14][15] couplings. The synchronization of spin-torque oscillators results in an enhancement of the emission power and an increase of the quality factor of the practical devices. In addition, new applications such as brain-inspired computing based on the synchronized spin-torque oscillators are proposed very recently [16][17][18][19].An attractive structure of spin-torque oscillator for practical applications is that consisting of a perpendicularly magnetized free layer and an in-plane magnetized pinned layer [20][21][22] because this type of spin-torque oscillator results in high emission power, narrow linewidth, and wide frequency tunability simultaneously. The oscillation properties of this type of spin-torque oscillator, such as the relation between the injected current and the oscillation frequency, as a single oscillator have been investigated both experimentally [22] and theoretically [23]. A possibility to excite a mutual synchronization in this type of spin-torque oscillators, however, has not been investigated yet.In this letter, a theoretical study on the mutual synchronization of spin-torque oscillators consisting of perpendicularly magnetized free layers and in-plane magnetized pinned layers is presented. We focus on the coupling of spin-torque oscillators through the current injection, and develop models of the coupling in the parallel and series circuits. Solving the Landau-Lifshitz-Gilbert (LLG) equation numerically, we show that two spin-torque oscillators indicate in-phase or antiphase synchronization depending on the way the oscillators are connected. An analytical theory clarifying the relation between the current, oscillation frequency, and phase difference is also developed. Both the numerical and analytical calculations indicate that the dependence of oscillation frequency on the current for both the parallel and series circuits are identical to that of a single spin-torque oscillator.The system under consideration is schematically shown in Fig. 1. There are two spin-torque oscillators, and each oscillator consists of a free layer F k (k = 1, 2) and a pinned ...

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“…These types of current-induced magnetization dynamics could potentially find use in novel functional spintronic devices [15] such as magnetic random access memories (MRAMs) [16], microwave oscillators [17,18], domain wall storage devices [19], and spin wave logic devices [20].…”

Section: Introductionmentioning

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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Phase-locking in double-point-contact spin-transfer devices

Cited by 490 publications

References 26 publications

Micromagnetic simulations of magnetization dynamics in a nanowire induced by a spin-polarized current injected via a point contact

Micromagnetic simulations of magnetization dynamics in a nanowire induced by a spin-polarized current injected via a point contact

Mutual synchronization of spin-torque oscillators consisting of perpendicularly magnetized free layers and in-plane magnetized pinned layers

Self-consistent calculation of spin transport and magnetization dynamics

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