Noise properties of ferromagnetic tunnel junctions

Nowak, E. R.; Merithew, R. D.; Weissman, M. B.; Bloom, I.; Parkin, S. S. P.

doi:10.1063/1.368936

Cited by 57 publications

(30 citation statements)

References 22 publications

(20 reference statements)

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“…Magnetic and nonmagnetic noises sources contribute to the noise of a magnetoresistive based devices. [1][2][3][4][5][6][7][8][9][10] These two noise processes can be identified by comparing the noise level and sensitivity at various applied magnetic fields. At low frequencies, these noise sources are either frequency independent or frequency dependent.…”

Section: Introductionmentioning

confidence: 99%

Dependence of noise in magnetic tunnel junction sensors on annealing field and temperature

Liou

Zhang

Russek

et al. 2008

Journal of Applied Physics

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The minimum detectable field of magnetoresistive sensors is limited by their intrinsic noise. Magnetization fluctuations are one of the crucial noise sources and are related to the magnetization alignment at the antiferromagnetic-ferromagnetic interface. In this study, we investigated the low frequency noise of magnetic tunnel junctions ͑MTJs͒ annealed in the temperature range from 265 to 305°C and magnetic fields up to 7 T, either in helium or hydrogen environments. Our results indicate that the magnetic fluctuators in these MTJs changed their frequency based on annealing field and temperature. The noise of the MTJs at low frequency can be reduced by annealing in high magnetic field ͑7 T͒ and further improved by annealing in a hydrogen environment.

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Section: Introductionmentioning

confidence: 99%

Dependence of noise in magnetic tunnel junction sensors on annealing field and temperature

Liou

Zhang

Russek

et al. 2008

Journal of Applied Physics

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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%

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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“…Furthermore, the short oxidation time has made the oxide barrier non-uniform and the process control difficult over an entire film. The results have often been a source for noise [8] and low dielectric breakdown [9] of the MTJ. On the other hand, recent reports suggest that large TMR can also be achieved if the barrier is prepared by radical oxidation, a process that involves energetically weak oxygen radicals [6].…”

Section: Introductionmentioning

confidence: 99%

Difference between chemical structures of the interface at the Al-oxide tunneling barrier prepared by plasma or by radical oxidation

Hong

Lee

Han

et al. 2007

Applied Surface Science

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Noise properties of ferromagnetic tunnel junctions

Cited by 57 publications

References 22 publications

Dependence of noise in magnetic tunnel junction sensors on annealing field and temperature

Dependence of noise in magnetic tunnel junction sensors on annealing field and temperature

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

Difference between chemical structures of the interface at the Al-oxide tunneling barrier prepared by plasma or by radical oxidation

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