Exchange-biased planar Hall effect sensor optimized for biosensor applications

Damsgaard, Christian Danvad; Freitas, Susana Vaz; Freitas, P. P.; Hansen, Mikkel Fougt

doi:10.1063/1.2830008

Cited by 35 publications

(28 citation statements)

References 9 publications

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“…32 However, in our previous studies, no significant indications of such a relaxation were observed for permalloy thicknesses up to 50 nm. 33 The edge relaxation becomes more energetically favorable when the exchangepinning is weakened, and therefore, the effective single domain shape anisotropy B sh is reduced. The combined effect of the shape anisotropy and reduction of B ex for the investigated sensor geometry and stack compositions was that no gain inS 0 could be obtained by increasing t FM above 20 nm (Fig.…”

Section: A Effects Of T Cu and T Fm On Sensor Behaviormentioning

confidence: 99%

Planar Hall effect bridge sensors with NiFe/Cu/IrMn stack optimized for self-field magnetic bead detection

Henriksen

Rizzi

Hansen

2016

Journal of Applied Physics

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Articles you may be interested inThe stack composition in trilayer Planar Hall effect bridge sensors is investigated experimentally to identify the optimal stack for magnetic bead detection using the sensor self-field. The sensors were fabricated using exchange-biased stacks Ni 80 Fe 20 (t FM )/Cu(t Cu )/Mn 80 Ir 20 (10 nm) with t FM ¼ 10, 20, and 30 nm, and 0 t Cu 0.6 nm. The sensors were characterized by magnetic hysteresis measurements, by measurements of the sensor response vs. applied field, and by measurements of the sensor response to a suspension of magnetic beads magnetized by the sensor self-field due to the sensor bias current. The exchange bias field was found to decay exponentially with t Cu and inversely with t FM . The reduced exchange field for larger values of t FM and t Cu resulted in higher sensitivities to both magnetic fields and magnetic beads. We argue that the maximum magnetic bead signal is limited by Joule heating of the sensors and, thus, that the magnetic stacks should be compared at constant power consumption. For a fixed sensor geometry, the figure of merit for this comparison is the magnetic field sensitivity normalized by the sensor bias voltage. In this regard, we found that sensors with t FM ¼ 20 nm or 30 nm outperformed those with t FM ¼ 10 nm by a factor of approximately two, because the latter have a reduced AMR ratio. Further, the optimum layer thicknesses, t Cu % 0.6 nm and t FM ¼ 20-30 nm, gave a 90% higher signal compared to the corresponding sensors with t Cu ¼ 0 nm. V C 2016 AIP Publishing LLC.

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Section: A Effects Of T Cu and T Fm On Sensor Behaviormentioning

confidence: 99%

Planar Hall effect bridge sensors with NiFe/Cu/IrMn stack optimized for self-field magnetic bead detection

Henriksen

Rizzi

Hansen

2016

Journal of Applied Physics

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“…1. For low fields along the -direction, the sensor output is (1) where is the sensor sensitivity [10]. The sensitivity for the sensors used in the experiments was found to V m/A .…”

Section: A System Design and Fabricationmentioning

confidence: 99%

Bead Capture on Magnetic Sensors in a Microfluidic System

et al. 2009

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Abstract-The accumulation of magnetic beads by gravitational sedimentation and magnetic capture on a planar Hall-effect sensor integrated in a microfluidic channel is studied systematically as a function of the bead concentration, the fluid flow rate, and the sensor bias current. It is demonstrated that the sedimentation flux is proportional to the bead concentration and has a power law relation to the fluid flow rate. The mechanisms for the bead accumulation are investigated and it is found that gravitational sedimentation dominates the bead accumulation, whereas the stability of the sedimented beads against the fluid flow is defined by the localized magnetic fields from the sensor.

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“…Consequently, the knee frequency is independent of the PHEB geometry, since D B has the same dependence on nlwt FM in both frequency regimes. Increasing t FM is the most effective measure to reduce D B , however, t FM can only be increased as long as the single-domain configuration is maintained -the limit being around 50 nm [25]. On the other hand, nlw can be increased several orders of magnitude without loosing the single-domain configuration.…”

Section: Figure 4 Herementioning

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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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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Exchange-biased planar Hall effect sensor optimized for biosensor applications

Cited by 35 publications

References 9 publications

Planar Hall effect bridge sensors with NiFe/Cu/IrMn stack optimized for self-field magnetic bead detection

Planar Hall effect bridge sensors with NiFe/Cu/IrMn stack optimized for self-field magnetic bead detection

Bead Capture on Magnetic Sensors in a Microfluidic System

Low-frequency noise in planar Hall effect bridge sensors

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