Bias and angular dependence of spin-transfer torque in magnetic tunnel junctions

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

doi:10.1103/physrevb.79.224416

Cited by 99 publications

(97 citation statements)

References 28 publications

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“…In this technique, a microwave current I ac applied to the nanowire excites magnetization dynamics in Py by the combined action of current-induced SO torques and the Oersted field from the current in Pt, and thereby generates AMR resistance oscillations at the frequency of the microwave drive 37 . Mixing of the current and resistance oscillations as well as variation of the timeaveraged sample resistance in response to the microwave drive 38,39 give rise to a direct voltage V dc that is measured as a function of magnetic field H applied to the sample. Peaks in V dc (H) arise from resonant excitation of spin wave eigenmodes of the nanowire.…”

Section: Resultsmentioning

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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Section: Resultsmentioning

confidence: 99%

Nanowire spin torque oscillator driven by spin orbit torques

et al. 2014

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“…In this technique, a microwave current I ac in the CPS generates a microwave magnetic field nearly perpendicular to the sample plane at the nanowire location and excites spin wave eigenmodes in the Py wire when the frequency of I ac coincides with its spin wave eigenmode frequencies. Excitation of the spin wave eigenmodes results in a small change δR in the time-average wire resistance that arises from anisotropic magnetoresistance (AMR) of Py 23,47,48 . This resistance variation is then measured as a function of H. Peaks in δR(H) such as those shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

Spin wave eigenmodes in transversely magnetized thin film ferromagnetic wires

et al. 2015

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We report experimental and theoretical studies of spin wave eigenmodes in transversely magnetized thin film Permalloy wires. Using broadband ferromagnetic resonance technique, we measure the spectrum of spin wave eigenmodes in individual wires as a function of magnetic field and wire width. Comparison of the experimental data to our analytical model and micromagnetic simulations shows that the intrinsic dipolar edge pinning of spin waves is negligible in transversely magnetized wires. Our data also quantify the degree of extrinsic edge pinning in Permalloy wires. This work establishes the boundary conditions for dynamic magnetization in transversely magnetized thin film wires for the range of wire widths and thicknesses studied, and provides a quantitative description of the spin wave eigenmode frequencies and spatial profiles in this system as a function of the wire width.

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“…We estimated θ from the assumption, that the resistance R of the MTJ changes as follows: where R AP and R P are the resistance of the MTJ for an antiparallel and parallel alignment of the FL and RL magnetization, respectively. In order to obtain the clearest STT results, 13 the strength and angle of the external magnetic field was adjusted so that magnetization of the FL is perpendicular to the magnetization of the RL (θ = 90 • ). The magnitude of the rf input signal, connected to the MTJ through the capacitive lead of a bias tee, was fixed to −15 dBm.…”

Section: Methodsmentioning

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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Bias and angular dependence of spin-transfer torque in magnetic tunnel junctions

Cited by 99 publications

References 28 publications

Nanowire spin torque oscillator driven by spin orbit torques

Nanowire spin torque oscillator driven by spin orbit torques

Spin wave eigenmodes in transversely magnetized thin film ferromagnetic wires

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

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