Noise and magnetic domain fluctuations in spin-valve GMR heads

Hardner, H. T.; Hurben, M. J.; Tabat, N.

doi:10.1109/20.800900

Cited by 34 publications

(10 citation statements)

References 7 publications

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“…[11][12][13] Spin-transfer-induced RTS at hertz to kilohertz rates has also been observed previously 14 for systems in which two well-defined magnetostatic states are accessible, i.e., when the applied field H app is less than H c , the coercive field of a patterned device with uniaxial anisotropy. In this case, the spin-transfer current modifies the thermally activated fluctuation rate between the two states.…”

mentioning

confidence: 62%

Large-angle, gigahertz-rate random telegraph switching induced by spin-momentum transfer

et al. 2004

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We show that a spin-polarized dc current passing through a small magnetic element induces two-state, random telegraph switching of the magnetization via the spin-momentum transfer effect. The resistances of the states differ by up to 50% of the change due to complete magnetization reversal. Fluctuations are seen for a wide range of currents and magnetic fields, with rates that can exceed 2 GHz, and involve collective motion of a large volume ͑10 4 nm 3 ͒ of spins. Switching rate trends with field and current indicate that increasing temperature alone cannot explain the dynamics. The rates approach a stochastic regime wherein dynamics are governed by both precessional motion and thermal perturbations.

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mentioning

confidence: 62%

Large-angle, gigahertz-rate random telegraph switching induced by spin-momentum transfer

et al. 2004

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“…5,6 The latter can be qualified by either large noise asymmetry swing with sweeping bias current or nonwhite noise spectrum. 6 Since Johnson noise and magnetic noise is expected to increase at elevated temperature, GMR element heating was monitored by head resistance increase.…”

Section: Methodsmentioning

confidence: 99%

Analysis of magnetic noise in lead overlaid giant magnetoresistive read heads

Zhang

Huai

Lederman

2002

Journal of Applied Physics

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Thermally induced magnetic noise in giant magnetoresistive (GMR) read heads was characterized with both contiguous junction and lead overlaid design using an integrated spectral method. At 0.25 μm magnetic read width and 4 mA bias current, magnetic noise is twice as large as Johnson noise for lead overlaid design, while it is comparable with Johnson noise for contiguous junction design. The head signal-to-noise ratio gain of 2–3 dB with lead overlaid design is less than an amplitude gain of 50%–100% since it is limited by increased magnetic noise, which roughly scales with amplitude. Magnetic noise increases with bias current at a much faster rate than Johnson noise. Higher magnetic noise is attributed to weaker longitudinal bias field associated with the lead overlaid design. Fortunately, magnetic noise does not limit system level signal to noise ratio since media transition noise is dominant. However, it is projected that magnetic noise will account for an increased portion of total noise power at higher areal densities.

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“…In larger sensors (several microns across), relatively complex measurement and signal processing schemes (e.g., a combination of differential measurement, alternating current (ac) sensing, ac magnetic fields, and direct current biasing fields) is needed to achieve adequate detection levels. Larger sensors also suffer from domain wall noise, limiting the ultimate resolution/sensitivity of the sensor [ 26 ]. Furthermore, sensing by large sensors requires a larger number of smaller particles spread across the sensor surface to achieve sufficiently high signal-to-noise ratios (SNRs).…”

Section: Introductionmentioning

confidence: 99%

Ultrasensitive Magnetic Nanoparticle Detector for Biosensor Applications

Liang

Chang

Qiu

et al. 2017

Sensors

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Ta/Ru/Co/Ru/Co/Cu/Co/Ni80Fe20/Ta spin-valve giant magnetoresistive (GMR) multilayers were deposited using UHV magnetron sputtering and optimized to achieve a 13% GMR ratio before patterning. The GMR multilayer was patterned into 12 sensor arrays using a combination of e-beam and optical lithographies. Arrays were constructed with 400 nm × 400 nm and 400 nm × 200 nm sensors for the detection of reporter nanoparticles. Nanoparticle detection was based on measuring the shift in high-to-low resistance switching field of the GMR sensors in the presence of magnetic particle(s). Due to shape anisotropy and the corresponding demag field, the resistance state switching fields were significantly larger and the switching field distribution significantly broader in the 400 nm × 200 nm sensors as compared to the 400 nm × 400 nm sensors. Thus, sensor arrays with 400 nm × 400 nm dimensions were used for the demonstration of particle detection. Detection of a single 225 nm Fe3O4 magnetic nanoparticle and a small number (~10) of 100 nm nanoparticles was demonstrated. With appropriate functionalization for biomolecular recognition, submicron GMR sensor arrays can serve as the basis of ultrasensitive chemical and biological sensors.

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Noise and magnetic domain fluctuations in spin-valve GMR heads

Cited by 34 publications

References 7 publications

Large-angle, gigahertz-rate random telegraph switching induced by spin-momentum transfer

Large-angle, gigahertz-rate random telegraph switching induced by spin-momentum transfer

Analysis of magnetic noise in lead overlaid giant magnetoresistive read heads

Ultrasensitive Magnetic Nanoparticle Detector for Biosensor Applications

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