AIP Advances (Jan 2021)

Highly-sensitive magnetic sensor for detecting magnetic nanoparticles based on magnetic tunnel junctions at a low static field

  • Z. Jin,
  • Thomas Myeongseok Koo,
  • Myeong Soo Kim,
  • M. Al-Mahdawi,
  • M. Oogane,
  • Y. Ando,
  • Young Keun Kim

DOI
https://doi.org/10.1063/9.0000189
Journal volume & issue
Vol. 11, no. 1
pp. 015046 – 015046-5

Abstract

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Magnetic sensors to detect magnetic nanoparticles (MNPs) towards biomedical applications require very high sensitivity at low magnetic fields. Here we report a magnetic sensor consisting of a magnetic tunnel junction (MTJ) with a synthetic antiferromagnetic free layer. This sensor exhibits a low magnetic anisotropy and sensitivities of over 18%/Oe at low fields in the range of 0 to 3 Oe. We employ superparamagnetic MNPs with a large diameter of 200 nm. The sensor’s transfer curves show the magnetoresistance (MR) variations as a function of MNP concentration. We demonstrate the detection capability of MNP amounts of below 500 ng and low MNP concentrations of 0.01, 0.1, and 1 mg/ml in solvents. This result suggests that the combination of high-sensitivity TMR sensors and large MNPs has a substantial potential for biomarker detection applications.