Detection of small magnetic fields using serial magnetic tunnel junctions with various geometrical characteristics

Zhenhu Jin, Yupeng Wang, Kosuke Fujiwara, Mikihiko Oogane, Yasuo Ando

Research output: Contribution to journalLetterpeer-review

1 Citation (Scopus)

Abstract

Thanks to their high magnetoresistance and integration capability, magnetic tunnel junction-based magnetoresistive sensors are widely utilized to detect weak, low-frequency magnetic fields in a variety of applications. The low detectivity of MTJs is necessary to obtain a high signal-to-noise ratio when detecting small variations in magnetic fields. We fabricated serial MTJ-based sensors with various junction area and free-layer electrode aspect ratios. Our investigation showed that their sensitivity and noise power are affected by the MTJ geometry due to the variation in the magnetic shape anisotropy. Their MR curves demonstrated a decrease in sensitivity with an increase in the aspect ratio of the free-layer electrode, and their noise properties showed that MTJs with larger junction areas exhibit lower noise spectral density in the low-frequency region. All of the sensors were able detect a small AC magnetic field (Hrms = 0.3 Oe at 23 Hz). Among the MTJ sensors we examined, the sensor with a square-free layer and large junction area exhibited a high signal-to-noise ratio (4792 ± 646). These results suggest that MTJ geometrical characteristics play a critical role in enhancing the detectivity of MTJ-based sensors.

Original languageEnglish
Article number5704
Pages (from-to)1-9
Number of pages9
JournalSensors (Switzerland)
Volume20
Issue number19
DOIs
Publication statusPublished - 2020 Oct 1

Keywords

  • Integrated magnetic sensor
  • Magnetic tunnel junction
  • Magnetoresistance sensor
  • Tunnel magnetoresistance

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry
  • Atomic and Molecular Physics, and Optics
  • Instrumentation
  • Electrical and Electronic Engineering

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