Low frequency noise peak near magnon emission energy in magnetic tunnel junctions

Li, D. L.; Yuan, Zhiyang; Feng, Jinchao; Han, X. F.; Coey, J. M. D.

doi:10.1063/1.4903278

Cited by 4 publications

(2 citation statements)

References 42 publications

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“…Since it appears only close to the magnetic phase transition at ∼118 K and disappears in the PM phase, it is evident that the Lorentzian component is associated with the magnetic phase transition and subsequent subtle change in its resistive behavior, as shown in Figure d. The nature of noise spectra is generally affected by the change in material phases in terms of electrical, structural, and magnetic properties. ,, When the material undergoes a phase change, the noise behavior can appear in the Lorentzian form due to the creation of a two-level system. In our case, at 118 K, the material undergoes a transition from the PM to the AFM phase.…”

Section: Resultsmentioning

confidence: 99%

“…The noise data on magnetic materials reveal the appearance of non-Gaussian RTS noise from thermally generated microscopic processes. , RTS noise involves the dominance of a single fluctuator of either electrical or magnetic origin that switches between two states. , The appearance of RTS noise has also been attributed to magnetic domain fluctuations and domain–domain interactions. , Among a few reported studies of LFN in AFM materials, it was found that thermally agitated magnetic noise in Co-based amorphous and polycrystalline alloys is of 1/ f type . Note that 1/ f and RTS noises are dominant noise sources in magnetic sensors and magnetic tunnel junctions, , and the noise data are generally used as a metric to measure the sensitivity and detectability of the device under varying magnetic fields …”

Section: Introductionmentioning

confidence: 99%

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Electronic Noise Spectroscopy of Quasi-Two-Dimensional Antiferromagnetic Semiconductors

Ghosh,

Nataj,

Kargar

et al. 2024

ACS Appl. Mater. Interfaces

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We investigated low-frequency current fluctuations, i.e., electronic noise, in FePS 3 van der Waals layered antiferromagnetic semiconductor. The noise measurements have been used as noise spectroscopy for advanced materials characterization of the charge carrier dynamics affected by spin ordering and trapping states. Owing to the high resistivity of the material, we conducted measurements on vertical device configuration. The measured noise spectra reveal pronounced Lorentzian peaks of two different origins. One peak is observed only near the Neél temperature, and it is attributed to the corresponding magnetic phase transition. The second Lorentzian peak, visible in the entire measured temperature range, has characteristics of the trap-assisted generation−recombination processes similar to those in conventional semiconductors but shows a clear effect of the spin order reconfiguration near the Neél temperature. The obtained results contribute to understanding the electron and spin dynamics in this type of antiferromagnetic semiconductors and demonstrate the potential of electronic noise spectroscopy for advanced materials characterization.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electronic Noise Spectroscopy of Quasi-Two-Dimensional Antiferromagnetic Semiconductors

Ghosh,

Nataj,

Kargar

et al. 2024

ACS Appl. Mater. Interfaces

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Spin-flip noise due to nonequilibrium spin accumulation

et al. 2016

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When current flows through a magnetic tunnel junction (MTJ), there is spin accumulation at the electrode-barrier interfaces if the magnetic moments of the two ferromagnetic electrodes are not aligned. Here we report that such nonequilibrium spin accumulation generates its own characteristic low frequency noise (LFN). Past work viewed the LFN in MTJs as an equilibrium effect arising from resistance fluctuations (SR) which a passively applied current (I) converts to measurable voltage fluctuations (SV = I 2 SR). We treat the LFN associated with spin accumulation as a nonequilibrium effect, and find that the noise power can be fitted in terms of the spin-polarized current by SI f = aI coth() − ab, resembling the form of the shot noise for a tunnel junction, but with current now taking the role of the bias voltage, and spin-flip probability taking the role of tunneling probability.Low frequency noise (LFN), often appearing as 1/f noise, is known to exist in both AlO x -based [1, 2] and MgO-based MTJs [3,4]. So far it was believed to be an equilibrium noise such as that observed in various semiconductor devices and disordered metal films [5][6][7]. With the assumption of equilibrium conductance or resistance fluctuations, mobility and carrier number fluctuations are the two apparent reasons while the microscopic origin varies in different cases. Although recently there was evidence [8] of excess shot noise induced by nonequilibrium spin accumulation which is proportional to the spin current, this observation seems irrelevant to the general perception that the LFN in magnetic materials is an essentially equilibrium phenomenon, which has no explicit connection to the spin-polarized current. Here we show this general perception is wrong and the LFN in MTJs is indeed driven by the spin-polarized current.It was through LFN measurements that Hardner et al.[9] first demonstrated the fluctuation-dissipation relation (FDR) in a magnetic system, metallic giant magnetoresistance (GMR) multilayers where the LFN peaks at magnetic fields maximizing the GMR derivative. The connection of the FDR to the LFN was later extended to MTJs [1] by assuming that magnetic fluctuations in the FM electrodes cause the fluctuations of resistance [10]. For this reason such field-sensitive LFN is also called magnetoresistive noise, sometimes simply called magnetic noise, which can be enhanced by annealing [11]. There is also a field-insensitive LFN ascribed to defect motion or charge trapping in the barrier and/or at the interface between the barrier and electrodes, sometimes called electronic noise, which decreases after annealing [12]. This electronic noise is also called barrier resistance noise, which is again an equilibrium effect.However, we find that MTJs driven far away from equilibrium can have a characteristic LFN distinct from that described by the FDR. Instead, in the presence of nonequilibrium spin accumulation, the noise power spectral density (PSD) of the LFN exhibits shot noise like dependence on the total current [13],where S I is ...

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Why Shot Noise Does Not Generally Detect Pairing in Mesoscopic Superconducting Tunnel Junctions

Niu,

Bastiaans,

et al. 2024

Phys. Rev. Lett.

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The shot noise in tunneling experiments reflects the Poissonian nature of the tunneling process. The shot-noise power is proportional to both the magnitude of the current and the effective charge of the carrier. Shot-noise spectroscopy thus enables us, in principle, to determine the effective charge q of the charge carriers of that tunnel. This can be used to detect electron pairing in superconductors: In the normal state, the noise corresponds to single electron tunneling (q=1e), while in the paired state, the noise corresponds to q=2e. Here, we use a newly developed amplifier to reveal that in typical mesoscopic superconducting junctions, the shot noise does not reflect the signatures of pairing and instead stays at a level corresponding to q=1e. We show that transparency can control the shot noise, and this q=1e is due to the large number of tunneling channels with each having very low transparency. Our results indicate that in typical mesoscopic superconducting junctions, one should expect q=1e noise and lead to design guidelines for junctions that allow the detection of electron pairing. Published by the American Physical Society 2024

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Low frequency noise peak near magnon emission energy in magnetic tunnel junctions

Cited by 4 publications

References 42 publications

Electronic Noise Spectroscopy of Quasi-Two-Dimensional Antiferromagnetic Semiconductors

Electronic Noise Spectroscopy of Quasi-Two-Dimensional Antiferromagnetic Semiconductors

Spin-flip noise due to nonequilibrium spin accumulation

Why Shot Noise Does Not Generally Detect Pairing in Mesoscopic Superconducting Tunnel Junctions

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