Magnetic tunnel junction sensors with pTesla sensitivity

Cardoso, Susana; Leitao, Diana C.; Gameiro, L.; Cardoso, Fabbryccio A. C. M.; Ferreira, Ricardo; Paz, Elvira; Freitas, P. P.

doi:10.1007/s00542-013-2035-1

Cited by 73 publications

(60 citation statements)

References 30 publications

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“…Currently, one of the most challenging areas targets the detection of lowintensity and low-frequency magnetic fields, such as the signals generated by brain activity (pT range below 100 Hz) [2], [3], requiring sensing devices with large signal-to-noise ratio (SNR) at room temperature. Sensors based on MgO magnetic tunnel junctions (MTJs) have already been used toward detectivity limits below pT/Hz 1/2 [4], [5]. However, at low frequencies the magnetoresistive sensor intrinsic noise is dominated by the 1/f noise component, which is responsible for the limitation of the sensor field detectivity.…”

Section: Introductionmentioning

confidence: 99%

Strategies for pTesla Field Detection Using Magnetoresistive Sensors With a Soft Pinned Sensing Layer

et al. 2015

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The detection of low-intensity and low-frequency signals requires magnetic sensors with enhanced sensitivity, low noise levels, and improved field detection at low operating frequencies. Two strategies to improve the detectivity levels of devices based on tunnel magnetoresistive sensors are demonstrated: 1) a large number of sensors connected in series or 2) an individual sensor with a large sensing area and integrated magnetic flux guides. State-of-the-art MgO-based magnetic tunnel junctions with a soft pinned sensing layer were used in this paper. For 952 sensors in series a sensitivity of 29.3%/mT and a detection level of 455 pT/Hz 1/2 were obtained at 100 Hz, whereas the integration of magnetic flux guides in a single sensor yielded a sensitivity of 138.3%/mT and a detection level of 576 pT/Hz 1/2 at the same frequency. These two strategies imply a large device footprint, being suitable when a high spatial resolution is not an application requirement.

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Section: Introductionmentioning

confidence: 99%

Strategies for pTesla Field Detection Using Magnetoresistive Sensors With a Soft Pinned Sensing Layer

et al. 2015

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“…For instance, ferromagnetic films may be employed in a large variety of magnetic sensors for different purposes [1][2][3]. Thus, the knowledge of the magnetization behavior under rf magnetic fields in these systems, its correlation with the structural and magnetic properties, as well as the role of the substrate on this behavior, is crucial to their applicability.…”

Section: Introductionmentioning

confidence: 99%

Mirroring the dynamic magnetic behavior of magnetostrictive Co/(Ag,Cu,Ta) multilayers grown onto rigid and flexible substrates

Agra

Gomes

Pace

et al. 2015

Journal of Magnetism and Magnetic Materials

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“…Figure 27 compares the detection levels as function of the sensing area obtained with different sensor layouts (single isolated sensors, arrays of sensors in series, or including MFCs) and also considering distinct types of MTJ stacks namely enclosing simple, SPM-like and soft-pinned sensing layers. Although the use of a soft-pinned sensing layer is an effective strategy to linearize sensors without increasing device footprint, detectivity values two orders of magnitude higher than those achieved using single sensors with simple sensing layers (∼ tens of pTesla) [85,90] 10601-p15…”

Section: Ptesla Detectivity Levelsmentioning

confidence: 99%

“…CoFeB/MgO/CoFeB-MTJ data obtained at operation point. Data marked with i from references [119,123,124] and ii is unpublished data from INESC-MN; * from reference [90]; + from reference [85]; & from reference [42]; α from reference [118]; β from reference [125]; δ is unpublished data from INESC-MN; σ from reference [41]; γ from reference [83]. Comparison between single sensors (solid shapes) and sensors with integrated MFCs (half-right shapes).…”

Section: Ptesla Detectivity Levelsmentioning

confidence: 99%

“…Square shapes represent data for micrometric structures from reference [41], either individual circular sensors (radius of 10, 28 and 36 µm) or series of 952 square sensors (50 × 50 µm 2 each); pentagonal shape from reference [83] measured at 10 Hz; left-triangle shape from reference [125]; right triangle shape from reference [118] whereas star shape represents data for nanometric circular MTJ pillars (radius 200 nm) from reference [42]. Simple sensing layer data from reference [90] (upward triangle) and [85] (downward triangle), and SPM-like sensing layer results from reference [92].…”

Section: Ptesla Detectivity Levelsmentioning

confidence: 99%

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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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Magnetic tunnel junction sensors with pTesla sensitivity

Cited by 73 publications

References 30 publications

Strategies for pTesla Field Detection Using Magnetoresistive Sensors With a Soft Pinned Sensing Layer

Strategies for pTesla Field Detection Using Magnetoresistive Sensors With a Soft Pinned Sensing Layer

Mirroring the dynamic magnetic behavior of magnetostrictive Co/(Ag,Cu,Ta) multilayers grown onto rigid and flexible substrates

Linearization strategies for high sensitivity magnetoresistive sensors

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