Magnetoresistive

Magnetoresistive refers to effects and devices in which electrical resistance changes in response to a magnetic field. The term encompasses several phenomena—AMR, GMR, TMR, and CMR—arising from spin-dependent transport and magnetic ordering in materials. These effects underpin sensors, read heads, and memories in modern electronics.

Anisotropic magnetoresistance occurs in ferromagnetic metals due to spin-orbit coupling, making resistance depend on the angle between current and magnetization. Typical changes are modest, but AMR enables compact magnetic sensors and position encoders used in a variety of devices.

Giant magnetoresistance appears in multilayer films combining ferromagnetic and nonmagnetic layers. The resistance varies with the relative alignment of the ferromagnetic layers, switching with magnetic fields or spin-polarized currents. GMR devices can show large changes and revolutionized data storage read heads.

Tunneling magnetoresistance occurs in magnetic tunnel junctions, where two ferromagnetic layers are separated by an insulating barrier. Spin-dependent tunneling yields large resistance changes when magnetizations switch, enabling high-sensitivity sensors and practical MRAM.

Colossal magnetoresistance is observed in some manganese oxide perovskites, where magnetic fields induce dramatic resistance reductions near magnetic transitions. While striking, CMR materials often require extreme conditions for practical use, and research continues into oxide spintronics.

Applications include automotive sensors, positioning systems, and memory technologies. Historically, AMR dates to the 19th century, while GMR and TMR were demonstrated in the 1980s–1990s, leading to rapid industrial impact.