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

doi:10.7567/JJAP.55.123001

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

ENG - Applied Physics

Research output: Contribution to journal › Article › peer-review

6 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 language	English
Article number	123001
Journal	Japanese Journal of Applied Physics
Volume	55
Issue number	12
DOIs	https://doi.org/10.7567/JJAP.55.123001
Publication status	Published - 2016 Dec

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

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.",

author = "Kyohei Ishikawa and Mikihiko Oogane and Kousuke Fujiwara and Junichi Jono and Masaaki Tsuchida and Yasuo Ando",

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T1 - Investigation of magnetic sensor properties of magnetic tunnel junctions with superparamagnetic free layer at low frequencies for biomedical imaging applications

AU - Ishikawa, Kyohei

AU - Oogane, Mikihiko

AU - Fujiwara, Kousuke

AU - Jono, Junichi

AU - Tsuchida, Masaaki

AU - Ando, Yasuo

PY - 2016/12

Y1 - 2016/12

N2 - 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.

AB - 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.

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

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