Low-drift giant magnetoresistive field sensor using modulation of free-layer magnetization direction

• Published in: Journal of physics. D, Applied physics Applied physics, 2011-06, Vol.44 (23), p.235003
• Main Authors: Wang, G A, Arai, S, Kato, T, Iwata, S
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Domain effects, magnetization curves, and hysteresis; Exact sciences and technology; Giant magnetoresistance; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Magnetic components, instruments and techniques; Magnetic properties and materials; Magnetization curves, magnetization reversal, hysteresis, barkhausen and related effects; Magnetotransport phenomena, materials for magnetotransport; Physics
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/44/23/235003

We report a field sensor, which senses the external field by detecting the change of frequency component in the modulated GMR output. The proposed sensor works in a closed-loop mode with negative feedback and the free-layer magnetization is modulated by an alternative field H ac (2.3 Oe). The sensor output ( V out ) is proportional to the applied external field ( H ex ) in the range from −1.5 to +1.5 Oe. V out is determined only by the feedback current, and has no direct relationship with the magnetoresistance ratio or the gains of the amplifiers. The proposed sensor exhibits a much lower temperature drift (about 1/50) compared with a typical magnetization rotation-type sensor and a further reduction in the drift can be achieved by improving the signal acquisition circuit; thus it can be used for high-precision dc field detection without any additional temperature compensation.