Instability analysis of spin-torque oscillator with an in-plane magnetized free layer and a perpendicularly magnetized pinned layer

Taniguchi, Tomohiro

doi:10.1103/physrevb.93.174401

Cited by 28 publications

(31 citation statements)

References 43 publications

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“…The critical switching current density of the MTJ with S-PMA can be obtained by employing the linearized LLG equation in the rotation coordinate, (X, Y, Z) 31,44 . The transformation matrix from the (x, y, z) coordinate to the (X, Y, Z) coordinates can be expressed as where θ and ϕ are the polar and azimuthal angles, respectively.…”

Section: Analytical Investigationmentioning

confidence: 99%

Critical switching current density of magnetic tunnel junction with shape perpendicular magnetic anisotropy through the combination of spin-transfer and spin-orbit torques

Kang

Shin

2021

Sci Rep

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Recently, magnetic tunnel junctions (MTJs) with shape perpendicular magnetic anisotropy (S-PMA) have been studied extensively because they ensure high thermal stability at junctions smaller than 20 nm. Furthermore, spin-transfer torque (STT) and spin-orbit torque (SOT) hybrid switching, which guarantees fast magnetization switching and deterministic switching, has recently been achieved in experiments. In this study, the critical switching current density of the MTJ with S-PMA through the interplay of STT and SOT was investigated using theoretical and numerical methods. As the current density inducing SOT ($$J_{\text {SOT}}$$ J SOT ) increases, the critical switching current density inducing STT ($$J_{\text {STT,c}}$$ J STT,c ) decreases. Furthermore, for a given $$J_{\text {SOT}}$$ J SOT , $$J_{\text {STT,c}}$$ J STT,c increases with increasing thickness, whereas $$J_{\text {STT,c}}$$ J STT,c decreases as the diameter increases. Moreover, $$J_{\text {STT,c}}$$ J STT,c in the plane of thickness and spin-orbit field-like torque ($$\beta$$ β ) was investigated for a fixed $$J_{\text {SOT}}$$ J SOT and diameter. Although $$J_{\text {STT,c}}$$ J STT,c decreases with increasing $$\beta$$ β , $$J_{\text {STT,c}}$$ J STT,c slowly increases with increasing thickness and increasing $$\beta$$ β . The power consumption was investigated as a function of thickness and diameter at the critical switching current density. Experimental confirmation of these results using existing experimental techniques is anticipated.

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Section: Analytical Investigationmentioning

confidence: 99%

Critical switching current density of magnetic tunnel junction with shape perpendicular magnetic anisotropy through the combination of spin-transfer and spin-orbit torques

Kang

Shin

2021

Sci Rep

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“…The existence of instability threshold of an in-plane magnetized free layer has been investigated previously [79,80,81,82,83,84,85], where the magnetization in the reference layer is fixed. Although it is difficult to extend these works to the two free layers system analytically, the existence of the instability threshold is qualitatively explained by using these single free layer models, as explained below.…”

Section: Threshold Currentmentioning

confidence: 99%

Synchronized, periodic, and chaotic dynamics in spin torque oscillator with two free layers

Taniguchi

2019

Journal of Magnetism and Magnetic Materials

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A phase diagram of the magnetization dynamics is studied by numerically solving the Landau-Lifshitz-Gilbert (LLG) equation in a spin torque oscillator consisting of asymmetric two free layers that are magnetized in in-plane direction. We calculated the dynamics for a wide range of current density for both low and high field cases, and found many dynamical phases such as synchronization, auto-oscillation with different frequencies, and chaotic dynamics. The observation of the synchronization indicates the presence of a dynamical phase which has not been found experimentally by using the conventional electrical detection method. The auto-oscillations with different frequencies lead to an oscillation of magnetoresistance with a high frequency, which can be measured experimentally. The chaotic and/or periodic behavior of magnetoresistance in a high current region, on the other hand, leads to a discontinuous change of the peak frequency in Fourier spectrum.

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“…In other words, p should be tilted in the yz plane to maximize the efficiency of the spin injection having the finite z-component of the spin polarization. This is an important difference from GMR or MTJ, where the ycomponent of the polarizer is unnecessary to excite an out-ofplane auto-oscillation [23][24][25][26][27][28][29][30][31][32]. We note that the tilted magnetic anisotropy has been investigated by making use of a higherorder anisotropy or an interlayer exchange coupling between two ferromagnets [34,35].…”

Section: Out-of-plane Auto-oscillation In In-plane Magnetized Free Layermentioning

confidence: 99%

“…At the end of this paper, let us discuss the application of the above result to magnetic recording. A spin torque oscillator (STO) consisting of an in-plane magnetized free layer and a perpendicularly magnetized pinned layer [23][24][25][26] is a candidate for the recording head of a hard disk drive using MAMR [28][29][30][31][32]45]. An oscillating magnetic field generated from the STO acts as a microwave field on the recording bit, and reduces the recording field [45].…”

Section: Application To Microwave Assisted Magnetization Reversalmentioning

confidence: 99%

“…Due to the restriction, the spin Hall effect, for example, cannot excite an out-of-plane autooscillation of a magnetization in a ferromagnet in the absence of an external magnetic field [16], which is a problematic issue in current magnetics. This is a disadvantage of the spin Hall geometry to giant magnetoresistive (GMR) system and magnetic tunnel junctions (MTJs), where the torque direction can be changed by controlling the magnetization direction in the pinned layer [17][18][19][20][21][22], and the out-of-plane auto-oscillation of the in-plane magnetized system has already been reported both experimentally and theoretically [23][24][25][26][27][28][29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

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Out-of-Plane Auto-Oscillation in Spin Hall Oscillator With Additional Polarizer

Taniguchi

2018

IEEE Trans. Magn.

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The theoretical investigation on magnetization dynamics excited by the spin Hall effect in metallic multilayers having two ferromagnets is discussed. The relaxation of the transverse spin in one ferromagnet enables us to manipulate the direction of the spin-transfer torque excited in another ferromagnet, although the spin-polarization originally generated by the spin Hall effect is geometrically fixed. Solving the Landau-Lifshitz-Gilbert-Slonczewski equation, the possibility to excite an out-of-plane auto-oscillation of an in-plane magnetized ferromagnet is presented. An application to magnetic recording using microwave-assisted magnetization reversal is also discussed.Index Terms-Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation, microwave-assisted magnetization reversal (MAMR), spin Hall effect, spin torque oscillator (STO), spintronics.

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Instability analysis of spin-torque oscillator with an in-plane magnetized free layer and a perpendicularly magnetized pinned layer

Cited by 28 publications

References 43 publications

Critical switching current density of magnetic tunnel junction with shape perpendicular magnetic anisotropy through the combination of spin-transfer and spin-orbit torques

Critical switching current density of magnetic tunnel junction with shape perpendicular magnetic anisotropy through the combination of spin-transfer and spin-orbit torques

Synchronized, periodic, and chaotic dynamics in spin torque oscillator with two free layers

Out-of-Plane Auto-Oscillation in Spin Hall Oscillator With Additional Polarizer

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