Spin torque oscillator for microwave assisted magnetization reversal

Taniguchi, Tomohiro

doi:10.7567/jjap.57.053001

Cited by 10 publications

(4 citation statements)

References 74 publications

(151 reference statements)

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“…( 19) to the magnetic field H in Eq. ( 1) 57 . The k component (k = x, y, z) of the random field is given by ℓ ).…”

Section: Discussionmentioning

confidence: 99%

Switching induced by spin Hall effect in an in-plane magnetized ferromagnet with the easy axis parallel to the current

Taniguchi

2020

Preprint

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Magnetization switching in a fine-structured ferromagnet of nanoscale by the spin-transfer torque excited via the spin Hall effect has attracted much attention because it enables us to manipulate the magnetization without directly applying current to the ferromagnet. However, the switching mechanism is still unclear in regard to the ferromagnet having an in-plane easy axis parallel to the current. Here, we develop an analytical theory of the magnetization switching in this type of ferromagnet, and reveal the threshold current formulas for a deterministic switching. It is clarified that the current should be in between a certain range determined by two threshold currents because the spin-transfer torque due to a large current outside the range brings the magnetization in an energetically unstable state, and causes magnetization precession around the hard axis.

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“…( 19) to the magnetic field H in Eq. ( 1) 57 . The k component (k = x, y, z) of the random field is given by ℓ ).…”

Section: Discussionmentioning

confidence: 99%

Switching induced by spin Hall effect in an in-plane magnetized ferromagnet with the easy axis parallel to the current

Taniguchi

2020

Preprint

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“…The introduction of terms of different symmetry and implicit dependence on the Gilbert damping is a non-obvious consequence of moving from the implicit LLGS equation to explicit form and often not discussed when performing numerical simulations [19][20][21][22], despite numerical packages solving the explicit form [7,8]. This complexity contributes to the confusion in the literature and also difficulty when interpreting experimental measurements between materials with different Gilbert damping constants.…”

Section: Theorymentioning

confidence: 99%

Spin-transfer and spin-orbit torques in the Landau–Lifshitz–Gilbert equation

Meo

Cronshaw²,

Jenkins³

et al. 2022

J. Phys.: Condens. Matter

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Dynamic simulations of spin-transfer and spin-orbit torques are increasingly important for a wide range of spintronic devices including magnetic random access memory, spin-torque nano-oscillators and electrical switching of antiferromagnets. Here we present a computationally efﬁcient method for the implementation of spin-transfer and spin-orbit torques within the Landau-Lifshitz-Gilbert equation used in micromagnetic and atomistic simulations. We consolidate and simplify the varying terminology of different kinds of torques into a physical action and physical origin that clearly shows the common action of spin torques while separating their different physical origins. Our formalism introduces the spin torque as an effective magnetic ﬁeld, greatly simplifying the numerical implementation and aiding the interpretation of results. The strength of the effective spin torque ﬁeld uniﬁes the action of the spin torque and subsumes the details of experimental effects such as interface resistance and spin Hall angle into a simple transferable number between numerical simulations. We present a series of numerical tests demonstrating the mechanics of generalised spin torques in a range of spin-tronic devices. This revised approach to modelling spin-torque effects in numerical simulations enables faster simulations and a more direct way of interpreting the results, and thus it is also suitable to be used in direct comparisons with experimental measurements or in a modelling tool that takes experimental values as input.

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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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Spin torque oscillator for microwave assisted magnetization reversal

Cited by 10 publications

References 74 publications

Switching induced by spin Hall effect in an in-plane magnetized ferromagnet with the easy axis parallel to the current

Switching induced by spin Hall effect in an in-plane magnetized ferromagnet with the easy axis parallel to the current

Spin-transfer and spin-orbit torques in the Landau–Lifshitz–Gilbert equation

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

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