Reading magnetic ink patterns with magnetoresistive sensors

Information storage and monitoring relies on sensitive transducers with high robustness and reliability. This paper shows a methodology enabling the qualification of magnetic sensors for magnetic pattern readout, in applications different than hard disk magnetic recording. A magnetic tunnel junction MTJ sensor was incorporated in a reader setup for recognition of the magnetization of patterned arrays made of CoCrPt thin films and magnetic ink. The geometry of the sensor (in particular, the footprint and vertical distance to the media) was evaluated for two sensor configurations. The readout conditions were optimized to cope for variable media field intensity, resulting from CoCrPt film or magnetic ink thickness, with fixed reading distance and dimensions of the pattern. The calibration of the ink magnetic signal could be inferred from the analytical calculations carried out to validate the CoCrPt results.