AMR is an abbreviation for Anisotropic Magneto Resistance. These are elements that have a function where the resistance decreases when a magnetic field is applied, and this function is dependent on the direction of the magnetic force lines applied to the element (anisotropic).
The material of the AMR element is a ferromagnetic metal that is an alloy of nickel, iron, and other metals.
Because the positive and negative sides have symmetric characteristics, the same operation is performed even if the north and south poles of the magnet are reversed. This characteristic is used to enable the gathering of high-accuracy, high-reliability data without making contact. Also, the capability of detecting without contact can be used in a wide range of applications such as open/close detection, rotation detection, and position detection.