Improved Signal-to-Noise Ratio in Current-Perpendicular-to-Plane Giant Magnetoresistance Sensors Using Strong Exchange-Biased Reference Layers

• Published in: IEEE magnetics letters Vol. 8; pp. 1 - 4
• Main Authors: Mihajlovic, Goran, Read, John C., Smith, Neil, van der Heijden, Paul, Tsang, Ching H., Childress, Jeffrey R.
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2017; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Annealing; CPP-GMR; Damping; Disk drives; exchange bias; Giant magnetoresistance; Giant magnetoresistance sensing devices; Hard disks; hard-disk drives; Magnetic field measurement; Magnetic heads; magnetic read head; Magnetic recording; Magnetic sensors; Magnetoresistance; Magnetoresistivity; Noise; Noise levels; Recording heads; Sensors; Signal to noise ratio; Spin electronics; spin torque; Temperature sensors
• ISSN: 1949-307X; 1949-3088
• DOI: 10.1109/LMAG.2016.2620119

We present experimental studies of simple-pinned current-perpendicular-to-the-plane giant magnetoresistance (CPP-GMR) sensors demonstrating large gains in signal-to-noise ratio from improvements in reference layer exchange pinning strength J k and magnetoresistance ratio AR/R. Significant increases in J k from 0.7 to 1.25 erg/cm 2 and AR/R from 7.5% to 13% are achieved by progressive improvements in the sensor structure. The improved sensors show lower spin transfer torque-induced noise due to stronger pinning and higher damping of the reference layer, both the consequence of increases in J k . This enables larger operational bias voltage, which along with higher AR/R, results in signal-to-noise gains of up to 6 dB in the recording heads. Our findings provide important insights for further development of CPP-GMR sensors in hard disk drives and other magnetic sensing applications.