GMR magnetic sensor using field modulation of magnetization direction and magnetic wall position

研制了三种利用巨磁电阻效应的自旋阀型磁传感器。在采用磁化方向调制方法的传感器中，自由层的方向受到流过铝导体的电流产生的交流磁场HAc的振荡调制。利用乘法器IC将GMR信号和HAC信号相乘，获得了低噪声输出。该传感器的灵敏度约为4MoE。在具有壁位调制方法的传感器的情况下，通过沿GMR元件的线形形成凹槽来钉扎磁壁。在巨磁电阻应变传感器中，通过磁致伸缩效应引起的自由层磁各向异性的变化，可以检测到施加交流磁场后自由层振荡调制幅度的变化。在5×10~(-4)的应变范围内，获得了与应变成线性关系的输出。

Three kinds of spin valve type magnetic sensors using giant magnetoresistance effect were developed. In case of the sensor with magnetization direction modulating method, the direction of a free layer was oscillatory modulated by ac magnetic field Hac produced by a current flowing through an Al conductor. Low noise output was obtained by multiplying the GMR signal and Hac signal using a multiplier IC. The sensitivity of the sensor was about 4 mOe. In case of the sensor with wall position modulating method, magnetic walls were pinned by forming notches along the line shape of the GMR element. In case of GMR strain sensor, the variation of amplitude of oscillatory modulation of the free layer by applying ac magnetic field can be detected through the variation of magnetic anisotropy of the free layer due to magneto-strictive effect. The linear output with the strain was obtained in strain range of 5x10-4.