Magnetic characteristics have been investigated for a magnetoresistive thin‐film sensor biased using a permanent magnet thin film. Here, Co‐Pt thin film is applied to the device as a bias film. Such microlithographed Co‐Pt thin films show the same magnetic properties as as‐sputtered films. Biasing strength depends on the permanent magnet film thickness, its composition or magnetic properties, and the biasing angle. The output of the sensor is very high.