Domain Wall Displacement Modulation GMR Sensors with Closed-Loop Current-Field Feedback

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  • Komuro K.
    Department of Electronics, Graduate School of Engineering, Nagoya University
  • Oshima D.
    Department of Electronics, Graduate School of Engineering, Nagoya University
  • Kato T.
    Department of Electronics, Graduate School of Engineering, Nagoya University Institute of Materials and Systems for Sustainability, Nagoya University

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<p>  A novel type of giant magneto-resistance (GMR) sensor utilizing domain wall displacement (DWD) modulation and a closed-loop current-field feedback technique was investigated. In this paper, a Ni80Fe20 free layer was used for the GMR sensor since the uniaxial anisotropy of Ni80Fe20 is smaller than that of the (Co90Fe10)92B8 used in the previous study, resulting in a larger wall displacement with a smaller field. When the domain wall was modulated by a modulation field Hmod = 94 μTrms, the sensitivity of the sensor increased to 2.6 mV/μT in open-loop mode compared with a sensitivity of 0.98 mV/μT for the sensor without Hmod. Moreover, a significant improvement in the linearity of the output was obtained by operating the DWD GMR sensor in closed-loop mode, and the sensitivity was also increased up to 4.2 mV/μT. The improvement in linearity is considered to be due to the suppression of the displacement of the average position of the domain walls by the current-field feedback. The noise floor of the output of the DWD GMR sensor under closed-loop operation was estimated to be 300 pT/Hz1/2 at 10 Hz.</p>

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