The detection directions of magnetic fields are different. In a Hall effect
sensor, when the
magnet is directly above the sensor, the axis between the north and south poles of the magnet is
perpendicular to the sensor. In an AMR, it is parallel to the sensor.
Because the magnetic force is strong near the north and south poles of the
magnet, when credit
card or other magnetic data is near, it could affect the card data. And so, AMR sensors are
advantageous when the magnet will not be placed perpendicularly in electronic devices such as
smartphones and notebook PCs. (This does not mean that magnetic data is not lost when a
horizontal placement is used.)
When the magnet position cannot be changed significantly, the AMR sensor
can be turned off by
the direction of the magnetic force lines. This can be used for applications in switches with
extremely short strokes and in rotation detection.
For details, see Differences Between AMR Sensors (Magnetic Switches) and Other
Systems.
Fundamentals of magnetic
sensors:
differences between AMR sensors (magnetic switches) and Hall effect sensors