Investigation of magnetic sensor properties of magnetic tunnel junctions with superparamagnetic free layer at low frequencies for biomedical imaging applications

Kyohei Ishikawa, Mikihiko Oogane, Kousuke Fujiwara, Junichi Jono, Masaaki Tsuchida, Yasuo Ando

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

The magnetic sensor properties of magnetic tunnel junctions (MTJs) with a superparamagnetic (SP) free layer were systematically investigated at low frequencies (<10 Hz). We prepared four varieties of MTJs with various SP properties by changing the annealing temperature. The temperature dependence of magnetoresistance curves and the signal/noise property at 285 K were evaluated. We found that the SP free layer has the advantage of detecting very small and low-frequency AC magnetic fields compared with a ferromagnetic free layer. The SP free layer strongly suppressed magnetic 1/f noise at low frequencies and expressed a very linear response to a small magnetic field. The obtained properties in MTJs with the SP free layer are suitable for detecting biomagnetic fields. The detectivity was 111 nT at low frequencies (from 0.1 to 10 Hz), which is one of the highest values in single-MTJ sensors.

Original languageEnglish
Article number123001
JournalJapanese journal of applied physics
Volume55
Issue number12
DOIs
Publication statusPublished - 2016 Dec

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)

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