Thin film magnetoresistive vector sensors with submicron gap width

Abstract

The size of gap between adjacent conducting strips In the folded resistor track of a thin film magnetoresistive sensor element has an important effect on its performance. Pattern fabrication methods using electron-beam lithography enable conductor spacings in the submicron range to be used. Sensors with smaller conductor spacing have an enhanced sensitivity and require a much smaller orthogonal bias field than devices made using conventional photolithography. The parameters for optimum linearity of the signal are considered in terms of the amount of harmonic distortion introduced by the sensor when its working range of ±1 oersted is swept by an input field of sinusoidal form. The distortion values are extremely low and the orthogonal field for best linearity is established to be close to that for peak sensitivity. immunity to fields at right angles to the measurement vector is also a function of the bias field: the optimum value in this case is about 75% of that for peak sensitivity. Noise measurements indicate that levels are sufficiently low to permit magnetic signals of less than one gamma to be detected.