magnetoresistivity

Magnetoresistivity is a property of materials that describes the change in their electrical resistance in response to an applied magnetic field. This phenomenon is of significant interest in both fundamental physics and practical applications, such as in magnetic sensors and data storage devices. The effect can be classified into two main types: anisotropic magnetoresistivity (AMR) and giant magnetoresistivity (GMR).

Anisotropic magnetoresistivity, first observed in the 19th century, occurs in ferromagnetic materials where the resistance changes with the orientation of the magnetization relative to the current direction. This effect is relatively small, typically on the order of a few percent.

Giant magnetoresistivity, discovered in the 1980s, is much more pronounced and occurs in multilayered structures consisting of ferromagnetic and non-magnetic layers. The resistance of these structures can change by several orders of magnitude when the magnetization of the ferromagnetic layers is aligned parallel or antiparallel. This effect is exploited in magnetic random-access memory (MRAM) and magnetic field sensors.

The magnetoresistive effect is typically characterized by the magnetoresistance ratio, which is the ratio of the resistance change to the original resistance. The magnetoresistive effect is influenced by several factors, including the material's composition, the strength and orientation of the magnetic field, and the temperature.

Magnetoresistivity has been extensively studied due to its potential for applications in data storage, magnetic sensors, and spintronics. Ongoing research aims to understand the underlying mechanisms and to develop new materials and structures with enhanced magnetoresistive properties.