TY - JOUR
T1 - Magnetic, magnetoresistive and low-frequency noise properties of tunnel magnetoresistance sensor devices with amorphous CoFeBTa soft magnetic layers
AU - Rasly, Mahmoud
AU - Nakatani, Tomoya
AU - Li, Jiangnan
AU - Sepehri-Amin, Hossein
AU - Sukegawa, Hiroaki
AU - Sakuraba, Yuya
N1 - Funding Information:
This work was partly supported by JSPS KAKENHI Grant Numbers 17H06152 and 20K04588.
Publisher Copyright:
© 2020 IOP Publishing Ltd.
PY - 2021/3/4
Y1 - 2021/3/4
N2 - Magnetic field sensors using the tunnel magnetoresistance (TMR) effect require linear resistance-magnetic field (R-H) response curves with small hysteresis, for which the soft magnetic property of the free layer (FL) is critical. In this work, we investigated amorphous CoFeBTa (CFBT) as a soft magnetic layer of the FL of CoFeB/MgO/CoFeB-based magnetic tunnel junctions in view of magnetic, TMR, and low-frequency noise properties. A two-step annealing process enabled an orthogonal magnetization configuration between the FL and the reference layer, by which linear R-H curves with small hysteresis were realized. The change in the shape of the R-H curve depending on annealing temperature is explained by the Stoner-Wohlfarth model. The highest TMR ratio of ∼160% and sensitivity of ∼70%/mT were obtained with a CFBT (20 nm)/Ta (0.3 nm)/CoFeB (3 nm) FL. The noise of the TMR devices are dominated by 1/f noise below ∼10 kHz in frequency, which limits the detectivity (D) of the magnetic field of the sensor. The sensor devices patterned to 50 µm diameter circular shapes showed a minimum D of ∼2 nT/at 10 Hz, which is superior to the previously reported values for the TMR sensors with NiFe soft magnetic layers.
AB - Magnetic field sensors using the tunnel magnetoresistance (TMR) effect require linear resistance-magnetic field (R-H) response curves with small hysteresis, for which the soft magnetic property of the free layer (FL) is critical. In this work, we investigated amorphous CoFeBTa (CFBT) as a soft magnetic layer of the FL of CoFeB/MgO/CoFeB-based magnetic tunnel junctions in view of magnetic, TMR, and low-frequency noise properties. A two-step annealing process enabled an orthogonal magnetization configuration between the FL and the reference layer, by which linear R-H curves with small hysteresis were realized. The change in the shape of the R-H curve depending on annealing temperature is explained by the Stoner-Wohlfarth model. The highest TMR ratio of ∼160% and sensitivity of ∼70%/mT were obtained with a CFBT (20 nm)/Ta (0.3 nm)/CoFeB (3 nm) FL. The noise of the TMR devices are dominated by 1/f noise below ∼10 kHz in frequency, which limits the detectivity (D) of the magnetic field of the sensor. The sensor devices patterned to 50 µm diameter circular shapes showed a minimum D of ∼2 nT/at 10 Hz, which is superior to the previously reported values for the TMR sensors with NiFe soft magnetic layers.
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U2 - 10.1088/1361-6463/abc2f5
DO - 10.1088/1361-6463/abc2f5
M3 - Article
AN - SCOPUS:85098272607
VL - 54
JO - Journal Physics D: Applied Physics
JF - Journal Physics D: Applied Physics
SN - 0022-3727
IS - 9
M1 - 095002
ER -