位相差計測による高周波キャリア型薄膜センサの評価(計測・高周波デバイス)

概要

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The impedance of a magnetic thin film changes when a magnetic field is applied. The high-frequency carrier magnetic field sensor, also called a GMI sensor, employs this phenomenon as its principle; it acts as previously a high-sensitivity magnetic field sensor. We detected the impedance by an amplitude-modulation method. As changing the impedance also changes a phase difference, we directed our attention to this phenomenon and measured the magnetic field by measuring the phase difference. The sensor element used was a meander pattern (thickness: 4.1 μm, length: 1 mm, width: 20 μm, unit distance: 50 μm, number of turns: 3), which was fabricatcd on a CoNbZr thin film by a lift-off process. The high frequency of the carrier signal made it difficult to measure the phase difference correctly. We converted the carrier frequency to a low frequency by the dual-mixer time-difference method and calculated the phase difference by measuring interval time. The best rate of change is 5.24 degrees/Oe at 7.8 Oe when the carrier frequency is 158 MHz. As the jitter error of this system is 5.51×l0^<-4> degree and the sampling rate is 1 ksample/sec, the resolution of this system is 3.32 × 10^<-6> Oe/√Hz.
社団法人日本磁気学会の論文
2004-05-01