Scientific Reports (Jan 2021)

Two-dimensional arrays of vertically packed spin-valves with picoTesla sensitivity at room temperature

  • Marilia Silva,
  • Fernando Franco,
  • Diana C. Leitao,
  • Susana Cardoso,
  • Paulo P. Freitas

DOI
https://doi.org/10.1038/s41598-020-79856-0
Journal volume & issue
Vol. 11, no. 1
pp. 1 – 10

Abstract

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Abstract A new device architecture using giant magnetoresistive sensors demonstrates the capability to detect very low magnetic fields on the pT range. A combination of vertically packed spin-valve sensors with two-dimensional in-plane arrays, connected in series and in parallel, delivers a final detection level of 360 pT/ $$\sqrt{Hz}$$ Hz at 10 Hz at room temperature. The device design is supported by an analytical model developed for a vertically packed spin-valve system, which takes into account all magnetic couplings present. Optimization concerning the spacer thickness and sensor physical dimensions depending on the number of pilled up spin-valves is necessary. To push the limits of detection, arrays of a large number of sensing elements (up to 440,000) are patterned with a geometry that improves sensitivity and in a configuration that reduces the resistance, leading to a lower noise level. The final device performance with pT detectivity is demonstrated in an un-shielded environment suitable for detection of bio-signals.