Presentation Information
[9a-N303-2]Extremely Sensitive Tunnel Magneto-resistive Sensor Using Magnetic Vortex Structures
〇(D)Seiya Takano1, Takafumi Nakano1,3, Takahide Kubota1, Kosuke Fujiwara4, Seiji Kumagai4, Hitoshi Matsuzaki4, Satoshi Sasaki5, Yutaka Higo5, Lui Sakai5, Masanori Hosomi5, Mikihiko Oogane1,2 (1.Graduate School of Engineering, Tohoku Univ., 2.CSIS, Tohoku Univ., 3.Research Center for Green X-Tech, Tohoku Univ., 4.Spin Sensing Factory Corporation, 5.Sony Semiconductor Solutions)
Keywords:
TMR sensor,magnetic vortex structure
Tunnel magnetoresistance (TMR) sensors based on magnetic tunnel junctions (MTJs) are highly sensitive and operate at room temperature. Sensitivity, defined as TMR ratio/2Hs [%/Oe], improves with a higher TMR ratio or lower saturation field (Hs). Prior work reported that miniaturizing the pinned layer in vortex-based TMR sensors reduces Hs, thus enhancing sensitivity. We fabricated sensors with a 10 μmφ free layer and a nanometer-scale pinned layer (40–100 nmφ) using sputtered multilayered MTJ films. After magnetic annealing, we found that decreasing the pinned layer size significantly reduced Hs and improved sensitivity. Notably, with an 80 nmφ pinned layer, we achieved Hs as low as 0.28 Oe and sensitivity as high as 268 %/Oe within ±0.3 Oe. Minor-loop conductance curves showed low coercivity and small hysteresis, indicating reversible vortex dynamics. These findings confirm that nanoscale vortex-based TMR sensors are promising for ultra-sensitive magnetic field detection.