Voltage-Induced Ferromagnetic Resonance in Magnetic Tunnel Junctions

Zhu, Jianguo; Katine, J. A.; Rowlands, Graham E.; Chen, Yu Jin; Duan, Zheng; Alzate, Juan G.; Upadhyaya, Pramey; Langer, Juergen; Amiri, Pedram Khalili; Wang, Kang L.; Krivorotov, I. N.

doi:10.1103/physrevlett.108.197203

Cited by 251 publications

(211 citation statements)

References 36 publications

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“…Optimization of MTJ performance for these applications requires quantitative evaluation of the spin torque (ST) vector [12], magnetic damping [13], voltagecontrolled magnetic anisotropy [14][15][16], and the spectrum of magnetic excitations of the MTJ [17,18]. A common techniques for quantitative measurements of these properties is ST ferromagnetic resonance (ST-FMR) [19,20].…”

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confidence: 99%

“…The amplitudes of the Lorentzians, V s and V a , are functions of the ST vector, magnetic parameters of the system [24], and voltage controlled magnetic anisotropy [16]. When the modulation field is small compared to the resonance linewidth in the field domain, the RMS voltage signalṼ mix (f ) measured by the lock-in amplifier is proportional to the first derivative of the rectified voltage V mix (f ) with respect to the modulated variable-the external magnetic field B:…”

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confidence: 99%

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Spin torque ferromagnetic resonance with magnetic field modulation

Gonçalves¹,

Barsukov²,

Chen³

et al. 2013

Applied Physics Letters

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We demonstrate a technique of broadband spin torque ferromagnetic resonance (ST-FMR) with magnetic field modulation for measurements of spin wave properties in magnetic nanostructures. This technique gives great improvement in sensitivity over the conventional ST-FMR measurements, and application of this technique to nanoscale magnetic tunnel junctions (MTJs) reveals a rich spectrum of standing spin wave eigenmodes. Comparison of the ST-FMR measurements with micromagnetic simulations of the spin wave spectrum allows us to explain the character of low-frequency magnetic excitations in nanoscale MTJs.The following article appeared in Appl. Phys. Lett. 103, 172406 (2013) and may be found at http://dx

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confidence: 99%

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confidence: 99%

Spin torque ferromagnetic resonance with magnetic field modulation

Gonçalves¹,

Barsukov²,

Chen³

et al. 2013

Applied Physics Letters

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“…This phenomenon, called the spin-torque diode effect, can be used as an RF-detector of very high sensitivity [7]. Recently, it has been shown that similar behavior can be achieved with alternatingvoltage-controlled magnetic anisotropy (VCMA) [8,9]. In this paper we propose a voltage tunable spin-torque diode, that is capable of sensing RF signals of different frequencies.…”

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confidence: 99%

Spin-torque diode radio-frequency detector with voltage tuned resonance

Skowroński

Frankowski

Wrona

et al. 2014

Applied Physics Letters

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We report on a voltage tunable radio-frequency (RF) detector based on a magnetic tunnel junction (MTJ). The spin-torque diode effect is used to excite and/or detect RF oscillations in the magnetic free layer of the MTJ. In order to reduce the overall in-plane magnetic anisotropy of the free layer, we take advantage of the perpendicular magnetic anisotropy at the interface between ferromagnetic and insulating layers. The applied bias voltage is shown to have a significant influence on the magnetic anisotropy, and thus on the resonance frequency of the device. This influence also depends on the voltage polarity. The obtained results are accounted for in terms of the interplay of spin-transfertorque and voltage-controlled magnetic anisotropy effects.Due to spin wave excitations, magnetic thin films can emit and/or absorb electromagnetic signals in a microwave frequency range determined by ferromagnetic resonance (FMR). In turn, radio-frequency (RF) signals can be produced in magnetic tunnel junctions (MTJs) via the spin-transfer-torque (STT) effect [1,2], where a spin polarized current excites magnetization precession with a frequency that depends, among others, on the magnetic anisotropy. This precession gives rise to an electric signal that can be used in various devices, like spin wave generators [3] or spin-torque oscillators [4,5]. The inverse effect, i.e., absorption of RF spin currents by a MTJ produces a detectable DC signal [6]. This phenomenon, called the spin-torque diode effect, can be used as an RF-detector of very high sensitivity [7]. Recently, it has been shown that similar behavior can be achieved with alternatingvoltage-controlled magnetic anisotropy (VCMA) [8,9]. In this paper we propose a voltage tunable spin-torque diode, that is capable of sensing RF signals of different frequencies. We achieved such a functionality by using a combination of the STT and VCMA effects. The former effect produces the DC voltage in response to AC current, while the latter one changes the resonance detection regime. In addition, using a specially designed MTJ, we are able to measure STT components in a volt- * Electronic address: skowron@agh.edu.pl age range of ±1 V, which to our knowledge is beyond the STT measurements published to date (up to ±0.5 V in Ref. [10]) and reveals a non-linear behavior of the in-plane STT component vs. bias voltage [11,12]. To achieve the above objective, we have investigated MTJs with the following multilayer structure: SiO 2 (substrate) / 5 Ta / 30 CuN / 3 Ta / 30 CuN / 3 Ta / 16 Pt 38 Mn 62 / 2.1 Co 70 Fe 30 / 0.9 Ru / 2.3 Co 40 Fe 40 B 20 / 1.6 MgO / 1-2 Co 40 Fe 40 B 20 / 10 Ta / 7 Ru (thickness in nm). By varying thickness of the CoFeB free layer (FL), we observed a transition from in-plane to perpendicular anisotropy at a critical thickness of t c ≈ 1.35 nm [13]. After deposition, the MTJs were annealed at 250 • C in an in-plane magnetic field of 0.4 T in order to set the exchange bias direction and to improve the crystallization of the ferromagnetic electrodes. For the transpor...

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“…In this case, the dependence of the detected DC voltage on the angle between the microwave magnetic field h(t), causing the effect, and the bias magnetic field H, magnetizing the magnetic metal, is qualitatively different from the angular dependence of the rectification voltage caused by the anisotropic magnetoresitance [2,14,16,17]. Moreover, the discovered PHE based rectification process produces DC voltage even in the case when the detected magnetization dynamics is associated with short-wavelength spatially non-uniform spin waves parametrically excited in the magnetic metal.…”

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confidence: 98%

Detection of Spin Waves in Permalloy Using Planar Hall Effect

et al. 2015

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Rectification of microwave oscillations of magnetization in a permalloy film is realized using planar Hall effect. Two different rectified signals are obtained: a signal from the linearly excited uniform magnetization precession at the frequency of the external pumping and a signal from the pairs of contra-propagating short-wavelength spin waves parametrically generated at a half of the pumping frequency. The second, most unusual, rectified signal is caused by the uniform component of the dynamic magnetization created due to the interference of the phase correlated pairs of parametric spin waves.The experimental investigations of phenomena caused by the spin-orbital interaction in magnetically ordered substances is one of the dominating directions in modern magnetism [1]. The spin-orbital effects like anisotropic magnetoresistance (AMR) [2], spin Hall [3] and inverse spin Hall [4] effects allow an experimentalist not only to detect the spin currents caused by linear and nonlinear the microwave magnetization dynamics (see e.g. Ref.[5]), but also to create pure spin currents that are sufficiently large to excite microwave auto-oscillations in magnetic metals [6]. Among the effects that allow one to electrically detect magnetization dynamics in magnetics the rectification effects, that are caused by the nonlinear coupling between the spin and charge dynamics and provide resultant signal in the form of a DC voltage, play a particularly important role, since they are sensitive not only to the geometric configuration of the detected microwave fields, but also to the phase and angular relations between the microwave fields and currents [7]. These effects can be used for the detailed probing of the magnetization dynamics in magnetic micro-and nano-structures [8] and, also, for the development of ultra-sensitive microwave detectors [9][10][11], demodulation of amplitude-modulated microwave signals [12], and for non-destructive testing [13].Here we present experimental evidence that another effect caused by the spin-orbital interaction, namely, the planar Hall effect (PHE) [14,15], can be successfully used for the detection and rectification of microwave signals exciting the oscillating magnetization dynamics in magnetic metals. In this case, the dependence of the detected DC voltage on the angle between the microwave magnetic field h(t), causing the effect, and the bias magnetic field H, magnetizing the magnetic metal, is qualitatively different from the angular dependence of the rectification voltage caused by the anisotropic magnetoresitance [2,14,16,17]. Moreover, the discovered PHE based rectification process produces DC voltage even in the case when the detected magnetization dynamics is associated with short-wavelength spatially non-uniform spin waves parametrically excited in the magnetic metal.Similarly to the conventional Hall effect, in case of the PHE the flow of the conduction electrons is deflected from the straight propagation path, but this deflection is not caused by the Lorentz force. It occurs due to t...

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Voltage-Induced Ferromagnetic Resonance in Magnetic Tunnel Junctions

Cited by 251 publications

References 36 publications

Spin torque ferromagnetic resonance with magnetic field modulation

Spin torque ferromagnetic resonance with magnetic field modulation

Spin-torque diode radio-frequency detector with voltage tuned resonance

Detection of Spin Waves in Permalloy Using Planar Hall Effect

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