Magnetoresistive sensors

Ferreira, Ricardo; Freitas, P. P.; Cardoso, Fabbryccio A. C. M.

doi:10.1088/0953-8984/19/16/165221

Cited by 382 publications

(227 citation statements)

References 75 publications

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“…The Hooge parameter, γ H , was calculated from Eq. (5) for each PHEB, giving a mean value of γ H =0.016, which is only one order of magnitude higher than typical values of γ H for well crystallized metallic films [22] and lower than for many magnetoresistive sensors [1,8,27,28]. Here, N C was estimated from the charge carrier density of Ni 80 Fe 20 , n Ni-Fe =17×10 28 m −3 [29], assuming that the majority of I was conducted though the NiFe layer given that ρ Ni-Fe <<ρ Mn-Ir <ρ Ta [30].…”

Section: Figure 4 Herementioning

confidence: 71%

“…Magnetic field sensors based either on the intrinsic anisotropic magnetoresistance (AMR) effect of ferromagnetic materials, or the giant magnetoresistance (GMR) and tunnelling magnetoresistance (TMR) effect of ferromagnetic/non-magnetic heterostructures are today utilized in many areas of science and technology [1,2]. With reports of magnetoresistance ratios of several hundred percent at room temperature, much work is presently focused on TMR sensors with the ambition to develop a magnetic field sensor with picotesla sensitivity [3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

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Low-frequency noise in planar Hall effect bridge sensors

Persson¹,

Bejhed²,

Nguyen³

et al. 2011

Sensors and Actuators A: Physical

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The low-frequency characteristics of planar Hall effect bridge sensors are investigated as function of the sensor bias current and the applied magnetic field. The noise spectra reveal a Johnson-like spectrum at high frequencies, and a 1/f-like excess noise spectrum at lower frequencies, with a knee frequency of around 400 Hz. The 1/f-like excess noise can be described by the phenomenological Hooge equation with a Hooge parameter of γ H =0.016. The detectivity is shown to depend on the total length, width and thickness of the bridge branches. Increasing the total length by a factor of 10 improves the detectivity by a factor of 10 1/2 . Moreover, the detectivity is shown to depend on the amplitude of the applied magnetic field, revealing a magnetic origin to part of the 1/f noise.

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Section: Figure 4 Herementioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Low-frequency noise in planar Hall effect bridge sensors

Persson¹,

Bejhed²,

Nguyen³

et al. 2011

Sensors and Actuators A: Physical

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“…[1][2][3][4][5][6][7][8][9] The record room temperature TMR of 604% is found in single-barrier MTJs ͑SMTJs͒ with a pseudo spin valve stack, 6 which is close to the theoretical maximum. 1,2 However, the TMR ratio in an MTJ falls off with increasing bias.…”

mentioning

confidence: 84%

1 / f noise in MgO double-barrier magnetic tunnel junctions

Diao

Feng

et al. 2011

Applied Physics Letters

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Low frequency noise has been investigated in MgO double-barrier magnetic tunnel junctions ͑DMTJs͒ with tunneling magnetoresistance ͑TMR͒ ratios up to 250% at room temperature. The noise shows a 1 / f frequency spectrum and the minimum of the noise magnitude parameter is 1.2ϫ 10 −10 m 2 in the parallel state for DMTJs annealed at 375°C. The bias dependence of noise and TMR suggests that DMTJs with MgO barriers can be useful for magnetic field sensor applications. © 2011 American Institute of Physics. ͓doi:10.1063/1.3562951͔The large tunneling magnetoresistance ͑TMR͒ in MgO barrier magnetic tunnel junctions ͑MTJ͒ has greatly improved the performance of spintronic devices, such as magnetic random access memories ͑MRAMs͒, sensors, and logic devices. [1][2][3][4][5][6][7][8][9] The record room temperature TMR of 604% is found in single-barrier MTJs ͑SMTJs͒ with a pseudo spin valve stack, 6 which is close to the theoretical maximum. 1,2 However, the TMR ratio in an MTJ falls off with increasing bias. 10 Double barrier MTJs ͑DMTJs͒ offer TMR of 105%-212% at room temperature 10-13 but bias dependence of TMR is reduced because the applied voltage is divided over two single barriers. This helps to preserve the high TMR ratio at high bias. 10 A high bias is needed to inject a sufficiently large critical current to facilitate spin transfer torque ͑STT͒ switching in magnetic nanopillars with MgO barriers, which is the basis for high-speed non-volatile STT-MRAM. 14 In conventional DMTJs with a thick free layer, TMR is often lower than that in SMTJs. [10][11][12][13] However, a DMTJ can potentially improve the signal-to-noise ratio of a magnetic field sensor due to the increase in output voltage compared to an SMTJ. Hence, the low frequency noise of DMTJs is worth exploring, in comparison with that of SMTJs. It has been previously reported that 1 / f noise dominates the low frequency response of MTJs. [15][16][17][18][19][20][21][22][23] The 1 / f noise can be characterized by a noise magnitude parameter ␣ = AfS V / V 2 , where A is the junction area, f is the frequency, S V is the noise power spectrum density, and V is the applied bias. 15 Recently, Guerrero et al. 24 suggested that 1 / f noise can be greatly reduced in field sensors, when a large number of MTJs are connected either in series or in parallel. However, devices constructed with a large number of MTJs may lack integrity and suffer from a much higher chance of failure. DMTJs may be able to halve the 1 / f noise without these drawbacks, opening up a way to reduce the noise.Until now, a few reports have been published on the low frequency noise in DMTJs with a thick free layer 12,20 but their TMR ratio of around 80%-120% is considerably less than we report here. Earlier studies of MgO DMTJs did not produce high TMR because the middle CoFeB layer remains amorphous after annealing. [10][11][12]20 The adjacent MgO barriers cannot absorb boron, which maintains the amorphous nature of CoFeB. 25 Here we investigate the low frequency noise in DMTJs, with TMR ratios as high...

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“…12a). Alternatively one can either resort to: i. use of the self-demagnetizing field of the sensing layer [76] (Fig. 12b, Sect.…”

Section: -P7mentioning

confidence: 99%

“…The magnetic part arises mainly from oscillations in the magnetization of the sensing layer, resulting from domain-wall pinning and depinning at defect sites (i.e., being maximum when the magnetization state is changing) [108,109]. For low frequencies, D can be expressed by [76]:…”

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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Magnetoresistive sensors

Cited by 382 publications

References 75 publications

Low-frequency noise in planar Hall effect bridge sensors

Low-frequency noise in planar Hall effect bridge sensors

1 / f noise in MgO double-barrier magnetic tunnel junctions

Linearization strategies for high sensitivity magnetoresistive sensors

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