Development of a sensitive and stable magnetoresistive sensor

The sensitivity and stability of a magnetoresistive (MR) sensor containing a permalloy thin film have been investigated. High-sensitivity sensors are usually disturbed by external noise, such as terrestrial magnetization. An MR sensor that can stably detect very weak magnetic fields under terrestrial magnetization has been developed using barber-pole-type biasing method. To sense very weak magnetic fields, a film thickness in the range of 300 to 500 Å and a wide pattern width are required for the MR. Stability depends on the sensitivity. It was confirmed that the MR sensor can stably detect very weak magnetic fields less than 1 Oe with proper film thickness and pattern shape