magnetoresistors

A magnetoresistor is a resistor whose electrical resistance changes in response to an external magnetic field. This phenomenon is known as magnetoresistance. There are several types of magnetoresistors, each based on different physical principles. The most common are made from ferromagnetic materials like permalloy. When a magnetic field is applied, the magnetic domains within these materials align, altering their resistance.

Another significant type is the giant magnetoresistance (GMR) sensor. GMR devices utilize thin layers of alternating ferromagnetic and non-magnetic materials. When a magnetic field changes the relative magnetization of the ferromagnetic layers, a substantial change in resistance occurs. Tunnel magnetoresistance (TMR) sensors, similar to GMR, exploit quantum mechanical tunneling of electrons through a thin insulating layer sandwiched between two ferromagnetic layers. The resistance is highly dependent on the relative alignment of the magnetization of the ferromagnetic layers. Anisotropic magnetoresistance (AMR) sensors, found in simpler devices, exhibit resistance changes due to the angle between the current flow and the magnetization direction within a single ferromagnetic material.

Magnetoresistors are widely used in various applications, including magnetic field sensors, read heads for hard disk drives, automotive sensors (like crankshaft position sensors), and non-contact switches. Their ability to detect magnetic fields with high sensitivity and accuracy makes them indispensable components in modern electronics.