Detection of Small Magnetic Fields Using Serial Magnetic Tunnel Junctions with Various Geometrical Characteristics
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 w...
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MDPI AG
2020-10-01
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| Series: | Sensors |
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| Online Access: | https://www.mdpi.com/1424-8220/20/19/5704 |
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| author | Zhenhu Jin Yupeng Wang Kosuke Fujiwara Mikihiko Oogane Yasuo Ando |
| author_facet | Zhenhu Jin Yupeng Wang Kosuke Fujiwara Mikihiko Oogane Yasuo Ando |
| author_sort | Zhenhu Jin |
| collection | DOAJ |
| description | 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 (<i>H</i><sub>rms</sub> = 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 <inline-formula><math display="inline"><semantics><mrow><mo>±</mo></mrow></semantics></math></inline-formula> 646). These results suggest that MTJ geometrical characteristics play a critical role in enhancing the detectivity of MTJ-based sensors. |
| first_indexed | 2024-03-10T15:47:30Z |
| format | Article |
| id | doaj.art-1cb39e7ed8a84b2d8f9f2a24b5e9dcd2 |
| institution | Directory Open Access Journal |
| issn | 1424-8220 |
| language | English |
| last_indexed | 2024-03-10T15:47:30Z |
| publishDate | 2020-10-01 |
| publisher | MDPI AG |
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| spelling | doaj.art-1cb39e7ed8a84b2d8f9f2a24b5e9dcd22023-11-20T16:18:32ZengMDPI AGSensors1424-82202020-10-012019570410.3390/s20195704Detection of Small Magnetic Fields Using Serial Magnetic Tunnel Junctions with Various Geometrical CharacteristicsZhenhu Jin0Yupeng Wang1Kosuke Fujiwara2Mikihiko Oogane3Yasuo Ando4Department of Applied Physics, Tohoku University, Sendai 980–8579, JapanDepartment of Applied Physics, Tohoku University, Sendai 980–8579, JapanSpin Sensing Factory Corporation, Sendai 980–0845, JapanDepartment of Applied Physics, Tohoku University, Sendai 980–8579, JapanDepartment of Applied Physics, Tohoku University, Sendai 980–8579, JapanThanks 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 (<i>H</i><sub>rms</sub> = 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 <inline-formula><math display="inline"><semantics><mrow><mo>±</mo></mrow></semantics></math></inline-formula> 646). These results suggest that MTJ geometrical characteristics play a critical role in enhancing the detectivity of MTJ-based sensors.https://www.mdpi.com/1424-8220/20/19/5704tunnel magnetoresistancemagnetic tunnel junctionmagnetoresistance sensorintegrated magnetic sensor |
| spellingShingle | Zhenhu Jin Yupeng Wang Kosuke Fujiwara Mikihiko Oogane Yasuo Ando Detection of Small Magnetic Fields Using Serial Magnetic Tunnel Junctions with Various Geometrical Characteristics Sensors tunnel magnetoresistance magnetic tunnel junction magnetoresistance sensor integrated magnetic sensor |
| title | Detection of Small Magnetic Fields Using Serial Magnetic Tunnel Junctions with Various Geometrical Characteristics |
| title_full | Detection of Small Magnetic Fields Using Serial Magnetic Tunnel Junctions with Various Geometrical Characteristics |
| title_fullStr | Detection of Small Magnetic Fields Using Serial Magnetic Tunnel Junctions with Various Geometrical Characteristics |
| title_full_unstemmed | Detection of Small Magnetic Fields Using Serial Magnetic Tunnel Junctions with Various Geometrical Characteristics |
| title_short | Detection of Small Magnetic Fields Using Serial Magnetic Tunnel Junctions with Various Geometrical Characteristics |
| title_sort | detection of small magnetic fields using serial magnetic tunnel junctions with various geometrical characteristics |
| topic | tunnel magnetoresistance magnetic tunnel junction magnetoresistance sensor integrated magnetic sensor |
| url | https://www.mdpi.com/1424-8220/20/19/5704 |
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