Electrical noise in hysteretic ferromagnet–insulator–ferromagnet tunnel junctions

Nowak, E. R.; Weissman, M. B.; Parkin, S. S. P.

doi:10.1063/1.123158

Cited by 115 publications

(85 citation statements)

References 13 publications

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“…Nowak, Weissman, and Parkin [302] measured the lowfrequency noise in a tunnel junction with two ferromagnetic electrodes separated by an insulating layer. They succeeded in extracting information on shot noise, and report sub-Poissonian suppression for low voltages, but they did not perform a systematic study of shot noise, and the situation, both theoretically and experimentally, is very far from being clear.…”

Section: A Coulomb Blockadementioning

confidence: 99%

Shot noise in mesoscopic conductors

2000

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Theoretical and experimental work concerned with dynamic fluctuations has developed into a very active and fascinating subfield of mesoscopic physics. We present a review of this development focusing on shot noise in small electric conductors. Shot noise is a consequence of the quantization of charge. It can be used to obtain information on a system which is not available through conductance measurements. In particular, shot noise experiments can determine the charge and statistics of the quasiparticles relevant for transport, and reveal information on the potential profile and internal energy scales of mesoscopic systems. Shot noise is generally more sensitive to the effects of electron-electron interactions than the average conductance. We present a discussion based on the conceptually transparent scattering approach and on the classical Langevin and BoltzmannLangevin methods; in addition a discussion of results which cannot be obtained by these methods is provided. We conclude the review by pointing out a number of unsolved problems and an outlook on the likely future development of the field.

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Section: A Coulomb Blockadementioning

confidence: 99%

Shot noise in mesoscopic conductors

2000

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“…It is remarkable that in our MTJs with a MgO barrier, ␣ is at least two orders of magnitude lower than in Al 2 O 3 MTJs at a given temperature. 4,6,8,9 It must also be noted that the V 2 dependence of the 1 / f noise power S V is linear ͑inset of Fig. 1 displays square-root values͒.…”

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confidence: 99%

“…Its origin is not fully understood, and, in particular, the influence of magnetization is still unclear although it is commonly observed that ␣ is higher in the APC than in the PC. 4,5 The quality of the metal-barrier interface may also play a role in the 1 / f noise. 4 The third component in MTJs is random telegraphic noise ͑RTN͒, namely, discrete fluctuators in the voltage-time traces associated with a Lorentzian-like spectrum.…”

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confidence: 99%

“…4,5 The quality of the metal-barrier interface may also play a role in the 1 / f noise. 4 The third component in MTJs is random telegraphic noise ͑RTN͒, namely, discrete fluctuators in the voltage-time traces associated with a Lorentzian-like spectrum. It is characterized by a strong sample-to-sample random of its amplitude and switching rate and it is interpreted either in terms of charge trapping or magnetic domain fluctuations.…”

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Noise in MgO barrier magnetic tunnel junctions with CoFeB electrodes: Influence of annealing temperature

Scola

Polovy

Fermon

et al. 2007

Applied Physics Letters

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Low frequency noise has been measured in magnetic tunnel junctions with MgO barriers and magnetoresistance values up to 235%. The authors investigated the noise for different degrees of crystallization and CoFeB / MgO interface quality depending on the annealing temperature. The authors report an extremely low 1 / f noise, compared to magnetic junctions with Al 2 O 3 barriers. The origin of the low frequency noise is discussed and it is attributed to localized charge traps with the MgO barriers. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2749433͔The resistance of a magnetic tunnel junction ͑MTJ͒ depends on the relative magnetization of the ferromagnetic layers: it is usually low in the parallel configuration ͑PC͒ and high in the antiparallel configuration ͑APC͒. This effect is used for storage in magnetic random access memory and is now being adopted for read heads in place of giant magnetoresistance ͑GMR͒ sensors. The prediction 1,2 and recent observation 3 of tunnel magnetoresistance ͑TMR͒ ratios ͓͑R AP − R P ͒ / R AP ͔ as high as 1000% in MTJs with MgO barrier make those devices very attractive candidates to outclass GMR in high-resolution sensors. However, a high TMR ratio is not enough to make a good magnetoresistive sensor, since its performance is determined by the sensitivity which is the output voltage per unit field divided by the voltage noise.The noise level is as important as the magnitude of the signal itself. From earlier studies on MTJs with Al 2 O 3 barriers, the noise can be traced back to three sources. The first is the frequency-independent thermal noise, which is an intrinsic property of a tunnel junction that defines the ultimate noise limit. Here, we will focus on the two other contributions to the noise, which may be reduced or even eliminated provided the appropriate parameters are known. At low frequencies, noise is dominated by a 1 / f component, which is analogous to 1 / f noise in conductors. It is quantified by the Hooge-like parameter ␣ = AfS V ͑f͒ / V 2 , expressed in units of area; A is the surface area of the junction, S V ͑f͒ the noise power spectrum, and V the voltage drop across the tunnel barrier. Its origin is not fully understood, and, in particular, the influence of magnetization is still unclear although it is commonly observed that ␣ is higher in the APC than in the PC. 4,5 The quality of the metal-barrier interface may also play a role in the 1 / f noise. 4 The third component in MTJs is random telegraphic noise ͑RTN͒, namely, discrete fluctuators in the voltage-time traces associated with a Lorentzian-like spectrum. It is characterized by a strong sample-to-sample random of its amplitude and switching rate and it is interpreted either in terms of charge trapping or magnetic domain fluctuations. 6 In this letter, we discuss low frequency noise properties of MTJs with a MgO barrier which exhibit TMR ratios up to 235%. Our focus is on the annealing temperature, which is the crucial parameter for a high TMR ratio. We discuss the origins of the noise, based on c...

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“…The total noise of a MTJ sensor has distinct contributions from thermal, shot, random telegraph and 1 / f electric and magnetic components, being the overall equation given by reference [107]. The minimum detectable field (D) of a sensor corresponds to the minimum value of applied field which causes a voltage output equal to the sensor intrinsic noise level (S V ).…”

Section: Ptesla Detectivity Levelsmentioning

confidence: 99%

Linearization strategies for high sensitivity magnetoresistive sensors

Silva

Leitao

Valadeiro

et al. 2015

Eur. Phys. J. Appl. Phys.

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Abstract. Ultrasensitive magnetic field sensors envisaged for applications on biomedical imaging require the detection of low-intensity and low-frequency signals. Therefore linear magnetic sensors with enhanced sensitivity low noise levels and improved field detection at low operating frequencies are necessary. Suitable devices can be designed using magnetoresistive sensors, with room temperature operation, adjustable detected field range, CMOS compatibility and cost-effective production. The advent of spintronics set the path to the technological revolution boosted by the storage industry, in particular by the development of read heads using magnetoresistive devices. New multilayered structures were engineered to yield devices with linear output. We present a detailed study of the key factors influencing MR sensor performance (materials, geometries and layout strategies) with focus on different linearization strategies available. Furthermore strategies to improve sensor detection levels are also addressed with best reported values of ∼40 pT/ √ Hz at 30 Hz, representing a step forward the low field detection at room temperature.

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Electrical noise in hysteretic ferromagnet–insulator–ferromagnet tunnel junctions

Cited by 115 publications

References 13 publications

Shot noise in mesoscopic conductors

Shot noise in mesoscopic conductors

Noise in MgO barrier magnetic tunnel junctions with CoFeB electrodes: Influence of annealing temperature

Linearization strategies for high sensitivity magnetoresistive sensors

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