Oscillation characteristics of zero-field spin transfer oscillators with field-like torque

Guo, Yuanyuan; Xue, Hai-Bin; Liu, Zhejie

doi:10.1063/1.4920941

Cited by 17 publications

(13 citation statements)

References 39 publications

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“…Stable out-of-plane dynamics are expected to occur in the region above the lines. The presence of dynamics only for positive currents was as expected, since only for this particular current direction (i.e., current favouring the AP state), the in-plane spin-transfer torque is efficient in overcoming the damping 18,34 (see the scheme of the "Sustained precession" case in Fig. 1(b)).…”

Section: Steady-state Precessionsupporting

confidence: 60%

Spin-transfer dynamics in MgO-based magnetic tunnel junctions with an out-of-plane magnetized free layer and an in-plane polarizer

et al. 2020

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Here, we present an analytical and numerical model describing the magnetization dynamics in MgO-based spin-torque nano-oscillators with an in-plane magnetized polarizer and an out-of-plane free layer. We introduce the spin-transfer torque asymmetry by considering the cosine angular dependence of the resistance between the two magnetic layers in the stack. For the analytical solution, dynamics are determined by assuming a circular precession trajectory around the direction perpendicular to the plane, as set by the effective field, and calculating the energy integral over a single precession period. In a more realistic approach, we include the bias dependence of the tunnel magnetoresistance, which is assumed empirically to be a piecewise linear function of the applied voltage. The dynamical states are found by solving the stability condition for the Jacobian matrix for out-of-plane static states. We find that the bias dependence of the tunnel magnetoresistance, which is an inseparable effect in every tunnel junction, exhibits drastic impact on the spin-torque nano-oscillator phase diagram, mainly by increasing the critical current for dynamics and quenching the oscillations at high currents. The results are in good agreement with our experimental data published elsewhere.

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Section: Steady-state Precessionsupporting

confidence: 60%

Spin-transfer dynamics in MgO-based magnetic tunnel junctions with an out-of-plane magnetized free layer and an in-plane polarizer

et al. 2020

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“…We also use numerical integration to analyze ensuing dynamical states; the magnitude of the precession motion is defined as the root mean square of the difference of the time-varying component of magnetization along the x -axis and its mean value, ( m x ( t ) − m x ) RMS . This magnitude is directly related to the experimentally measured output power, as the RF signal from STNOs is to given by the time varying projection of m along the magnetization of the reference layer 12,30 , in this case fixed along the x -direction (see Fig. 1(a)).…”

Section: Resultsmentioning

confidence: 99%

Tunnel magnetoresistance angular and bias dependence enabling tuneable wireless communication

Kowalska

Fukushima

Sluka

et al. 2019

Sci Rep

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Spin-transfer torques (STTs) can be exploited in order to manipulate the magnetic moments of nanomagnets, thus allowing for new consumer-oriented devices to be designed. Of particular interest here are tuneable radio-frequency (RF) oscillators for wireless communication. Currently, the structure that maximizes the output power is an Fe/MgO/Fe-type magnetic tunnel junction (MTJ) with a fixed layer magnetized in the plane of the layers and a free layer magnetized perpendicular to the plane. This structure allows for most of the tunnel magnetoresistance (TMR) to be converted into output power. Here, we experimentally and theoretically demonstrate that the main mechanism sustaining steady-state precession in such structures is the angular dependence of the magnetoresistance. The TMR of such devices is known to exhibit a broken-linear dependence versus the applied bias. Our results show that the TMR bias dependence effectively quenches spin-transfer-driven precession and introduces a non-monotonic frequency dependence at high applied currents. This has an impact on devices seeking to work in the ‘THz gap’ due to their non-trivial TMR bias dependences.

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“…Investigations on STNOs with perpendicularly magnetized free layer and parallelly magnetized pinned layer in the presence of an out-of-plane field show the possibility of (1) steady state precession with a maximum frequency of 6.3 GHz with a high power of 0.55 µW [15] and Q-factor 135 and (2) steady state precession with a maximum frequency of 45 GHz with a high Q-factor over 3000 and power 64 nW [16]. Without an out-of-plane field, the steady state precession is not possible for this configuration of STNO, and it can be induced by appropriate field-like torque [17,18].…”

Section: Introductionmentioning

confidence: 96%

Spin Torque Oscillations Triggered by In-plane Field

Arun,

Gopal,

Chandrasekar

et al. 2021

Preprint

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We study the dynamics of a spin torque nano oscillator that consists of parallelly magnetized free and pinned layers by numerically solving the associated Landau-Lifshitz-Gilbert-Slonczewski equation in the presence of a field-like torque. We observe that an in-plane magnetic field which is applied for a short interval of time (<1ns) triggers the magnetization to exhibit self-oscillations from low energy initial magnetization state. Also, we confirm that the frequency of oscillations can be tuned over the range ∼25 GHz to ∼72 GHz by current, even in the absence of field-like torque. We find the frequency enhancement up to 10 GHz by the presence of field-like torque. We determine the Q-factor for different frequencies and show that it increases with frequency. Our analysis with thermal noise confirms that the system is stable against thermal noise and the dynamics is not altered appreciably by it.

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Oscillation characteristics of zero-field spin transfer oscillators with field-like torque

Cited by 17 publications

References 39 publications

Spin-transfer dynamics in MgO-based magnetic tunnel junctions with an out-of-plane magnetized free layer and an in-plane polarizer

Spin-transfer dynamics in MgO-based magnetic tunnel junctions with an out-of-plane magnetized free layer and an in-plane polarizer

Tunnel magnetoresistance angular and bias dependence enabling tuneable wireless communication

Spin Torque Oscillations Triggered by In-plane Field

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