Magnetoresistive performances in exchange-biased spin valves and their roles in low-field magnetic sensing applications

• Main Authors: Luong, Van Su, Nguyen, Anh Tuan, Hoang, Quoc Khanh, Nguyen,Tuyet Nga, Nguyen,Anh Tue, Nguyen,Tuan Anh, Giap, Van Cuong
• Format: Article
• Language: English
• Published: Elsevier 2019
• Subjects: GMR; Giant magnetoresistance; Magnetic sensors; RFsputtering; Spin valve
• Online Access: http://repository.vnu.edu.vn/handle/VNU_123/64655; https://doi.org/10.1016/j.jsamd.2018.09.004
• Institution: Vietnam National University, Hanoi

The magnetoresistive properties of pinned spin valves (SV) and their roles in low-field sensing applications were characterized. The magnetoresistive parameters were extracted, including the exchange bias (Heb)field as a function of the iron content in theCoFelayerand theantiferromagnetic (AFM) thickness, the magnetoresistance (MR) ratio versus the spacer thickness, the coercivity (Hc)asa function of the seed layer, and the composite layer [NiFe/Co] used. These parameters are crucial in determining the features of the magnetic sensors. Eventually, the selected SVfilm structure of (Si/ SiO2)/Ta(50 Å)/[NiFe(30Å)/Co(15 Å)]/Cu(24 Å)/Co80Fe20(25 Å)/IrMn(100 Å)/Ta(50 Å)was found sig-nificant, and the SV elements were patterned using the lithographic lift-off method with the active cell dimensions of 2mm 150mm. To define a pinning axis, a cool-field anneal was applied at 250 Cfor 30 mininamagneticfield of 2 kOe. A Wheatstone half bridge was engineered using two SV elements and two external resistors. The operation point of the sensor was well tuned using a tiny permanent magnet. A sensitivity of 5 V/T was observed with a linear range of±2 mT. To demonstrate the performance of the designed sensor, a measurement of the Earth magneticfield was carried out. The engineered SV sensor finds its usefulness in low-field magnetometer and electronic compass applications