Current Modulation of Nanoconstriction Spin-Hall Nano-Oscillators

Zahedinejad, Mohammad; Awad, Ahmad A.; Dürrenfeld, Philipp; Houshang, Afshin; Yin, Yuli; Muduli, P. K.; Åkerman, Johan

doi:10.1109/lmag.2017.2671453

Cited by 26 publications

(16 citation statements)

References 183 publications

(242 reference statements)

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Section: Introductionmentioning

confidence: 99%

“…Superparamagnetism has been studied for many years [1][2][3], but is still of great interest today [4]. Superparamagnetic particles are used in many biomedical applications [5,6], mainly because the fluctuations minimize magnetically driven aggregation. Programmable superparamagnets could form the basis for a new type of probabilistic computing using magnetic tunnel junctions (MTJs) [7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…Superparamagnetic particles are used in many biomedical applications [5,6], mainly because the fluctuations minimize magnetically driven aggregation. Programmable superparamagnets could form the basis for a new type of probabilistic computing using magnetic tunnel junctions (MTJs) [7][8][9][10]. Superparamagnetism is also relevant to spintronic applications such as magnetic random access memory (MRAM) [11][12][13] and spin-torque oscillators (STOs) [14], where at small diameters stochastic fluctuations are undesirable but difficult to avoid.…”

Section: Introductionmentioning

confidence: 99%

“…The average fluctuation rate in traditional superparamagnets is controlled by temperature and magnetic field. When part of an electronic device, the frequency of these stochastic fluctuations may also be tuned by spin-transfer torque (STT) [14], spin-orbit torque, or voltage control of magnetic anisotropy [15]. Here we focus on Co-Fe-B superparamagnets that are most relevant for spintronics applications.…”

Section: Introductionmentioning

confidence: 99%

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Magnetoresistance Dynamics in Superparamagnetic Co−Fe−B Nanodots

et al. 2020

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Individual disk-shaped Co-Fe-B nanodots are driven into a superparamagnetic state by a spin-transfer torque, and their time-dependent magnetoresistance fluctuations are measured as a function of current. A thin layer of oxidation at the edges has a dramatic effect on the magnetization dynamics. A combination of experimental results and atomistic spin simulations shows that pinning to oxide grains can reduce the likelihood that fluctuations lead to reversal, and can even change the easy-axis direction. Exchange-bias loop shifts and training effects are observed even at room temperature after brief exposure to small fields. The results have implications for studies of core-shell nanoparticles and small magnetic tunnel junctions and spin-torque oscillators.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magnetoresistance Dynamics in Superparamagnetic Co−Fe−B Nanodots

et al. 2020

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“…The de-coupling of charge and spin currents opens up new device geometries, for example enabling exploitation of magnetic insulators 8 , and in the present study, allows optical access to the active region of the device.The generation of magnetic auto-oscillations requires a critical spin current density to be exceeded. Within the SHNO the injected charge current is concentrated within a small region of the heavy metal, either by overlaying thick needle-shaped nano-contacts (NCs) on the heavy metal layer , 5,[9][10][11][12][13] or by forming a nanoconstric-tion within the heavy metal/ ferromagnet bilayer [14][15][16][17][18][19] . SHNOs of both kinds have been studied by Brillouin Light Spectroscopy (BLS), microwave spectroscopy and micro-magnetic simulations.…”

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confidence: 99%

Time resolved imaging of the non-linear bullet mode within an injection-locked nano-contact spin Hall nano-oscillator

Spicer

Keatley

Dvornik

et al. 2018

Applied Physics Letters

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Time-resolved scanning Kerr microscopy (TRSKM) has been used to image precessional magnetization dynamics excited by a DC current within a nano-contact (NC) spin Hall nano-oscillator (SHNO). Injection of a radio frequency (RF) current was used to phase lock the SHNO to the TRSKM. The out of plane magnetization was detected by means of the polar magneto optical Kerr effect (MOKE). However, longitudinal MOKE images were dominated by an artifact arising from the edges of the Au NCs. Time resolved imaging revealed the simultaneous excitation of a non-linear 'bullet' mode at the centre of the device, once the DC current exceeded a threshold value, and ferromagnetic resonance (FMR) induced by the RF current. However, the FMR response observed for sub-critical DC current values exhibits an amplitude minimum at the centre, which is attributed to spreading of the RF spin current due to the reactance of the device structure. This FMR response can be subtracted to yield images of the bullet mode. As the DC current is increased above threshold, the bullet mode appears to increase in size, suggesting increased translational motion. The reduced spatial overlap of the bullet and FMR modes, and this putative translational motion, may impede the injection locking and contribute to the reduced locking range observed within NC-SHNO devices. This illustrates a more general need to control the geometry of an injection-locked oscillator so that the autonomous dynamics of the oscillator exhibit strong spatial overlap with those resulting from the injected signal.Within a spin torque oscillator (STO), magnetic autooscillations, with MHz to GHz frequencies, are driven by the spin transfer torque (STT) associated with injection of DC spin current. Their frequency and amplitude can be tuned via either the DC electrical bias current or an applied magnetic field, while the magnetoresistance of the constituent materials leads to the generation of voltage oscillations. STOs have strong potential for magnetic sensing, signal processing, and neurmorphic computing applications 1,2 . The ability to lock the frequency and phase of the STO to an injected RF signal is an important property within applications, while arrays of STOs promise increased output power through mutual synchronization. However it is first necessary to understand the character of the underlying magnetization dynamics. More specifically, the dynamics excited by both DC and RF currents must be determined if the conditions required for phase-locking are to be fully understood.Within a spin Hall nano-oscillator (SHNO) the Spin Hall effect (SHE) 3,4 drives a pure spin current from a heavy metal with large spin-orbit interaction into a ferromagnet layer 5-7 . The de-coupling of charge and spin currents opens up new device geometries, for example enabling exploitation of magnetic insulators 8 , and in the present study, allows optical access to the active region of the device.The generation of magnetic auto-oscillations requires a critical spin current density to be exceeded. Within t...

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