Shielded magnetoresistive head for high density recording

Yamada, Kazuhiko; Maruyama, Takao; Tatsumi, Toru; Suzuki, T.; Shimabayashi, K.; Motomura, Y.; Aoyama, M.; Urai, H.

doi:10.1109/20.102882

Cited by 9 publications

(2 citation statements)

References 17 publications

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“…LB fields in the perpendicular direction of the measurement direction (pinned layer direction) can be used for proper sensor operation, suppressing the multidomain formation that induces Barkhausen noise in the sensor sensing layer. 3,4 Different approaches have been applied to magnetoresistive sensors to create an external field to the sensing layer based either on permanent magnets (PM) or ferromagnetic films exchange coupled by antiferromagnets. 5,6 Typically, additional process steps are required to pattern and to set (usually by anneal) the exchange bias direction of the LB field.…”

mentioning

confidence: 99%

Low aspect ratio micron size tunnel magnetoresistance sensors with permanent magnet biasing integrated in the top lead

Chaves

Cardoso

Ferreira

et al. 2011

Journal of Applied Physics

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Optimized single magnetic bead detection requires magnetic sensors with an improved field detection limit and a sensor area matching the bead cross section (micron size spatial resolution). This work shows that square micron sized tunnel magnetoresistance sensors can be fabricated with integrated longitudinal permanent magnet (PM) biasing that show a linearized field response and low noise. PMs (Co66Cr16Pt18) were integrated in the top lead of an AlOx based magnetic tunnel junction sensor for transfer curve linearization. Sensors patterned with dimensions down to 3 × 3 μm2 present field detection limits of 6 nT/Hz0.5 and 3 nT/Hz0.5 at 10 kHz and 500 kHz, respectively, corresponding to a field sensitivity of 1.8% per mT (linear field detection range ΔB = −8 mT + 8 mT) and αH = 3.9 ± 0.3 × 10−10 μm2 (RxA = 1.9 kΩ μm2).

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mentioning

confidence: 99%

Low aspect ratio micron size tunnel magnetoresistance sensors with permanent magnet biasing integrated in the top lead

Chaves

Cardoso

Ferreira

et al. 2011

Journal of Applied Physics

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“…Such a LB field suppresses multidomain formation in the sensing layer which induces Barkhausen noise in the sensor transfer curve [15,18]. Distinct approaches can be used, such as incorporated permanent magnets (PM) or exchange coupled free layers [19,20].…”

Section: Biasing With Permanent Magnetsmentioning

confidence: 99%

Magnetic tunnel junction sensors with pTesla sensitivity for biomedical imaging

Cardoso¹,

Gameiro²,

Leitao³

et al. 2013

SPIE Proceedings

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Ultrasensitive magnetic field sensors at low frequencies are necessary for several biomedical applications. Suitable devices can be achieved by using large area magnetic tunnel junction sensors combined with permanent magnets to stabilize the magnetic configuration of the free layer and improve linearity. However, further increase in sensitivity and consequently detectivity are achieved by incorporating also soft ferromagnetic flux guides. A detailed study of tunnel junction sensors with variable areas and aspect ratios is presented in this work. In addition, the effect in the sensors transfer curve, namely in their coercivity and sensitivity, as a consequence of the incorporation of permanent magnets and flux guides is also thoroughly discussed. Using sensors with a tunnel magnetoresistance of ~200 %, incorporating both permanent magnets and flux guides sensitivities of 220-260 %/mT were obtained for high aspect ratio sensors, increasing to values larger than ~2000%/mT for large areas and low aspect ratio sensors. Measured noise levels of the final device at 10 Hz yield 3.9×10 -17 V 2 /Hz, leading to an improved lowest detectable field of ~ 94 pT/ Hz 0.5 .

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