Magnetometers using magnetoresistance methods: Basically, AMR is about detecting between the direction of electric current and magnetization in the presence of magnetization. Upon being exposed to an external magnetic field, the spins of the electron orbitals making up the material redistribute themselves.

The main application of GMR is in magnetic field sensors, which are used to read data in hard disk drives, biosensors, microelectromechanical systems (MEMS) and other devices. GMR multilayer structures are also used in magnetoresistive random-access memory (MRAM) as cells that store one bit of information.

In simplified form, a magnetoresistive sensor functions as follows: An object with its own magnetic field approaches the sensor. As a result, the electrical resistance changes. This makes it possible to detect at what angle the external magnetic field (and thus the object) is positioned in relation to the sensor.

Working Principle of Magnetoresistor. In the presence of the magnetic field, the direction of the current becomes changes, and it flows in the opposite direction. The indirect path of the current increases the mobility of their charge carrier which causes the collision.

Applications. Spin valves are used in magnetic sensors and hard disk read heads. They are also used in magnetic random access memories (MRAM).

Magnetoresistance is the tendency of a material (often ferromagnetic) to change the value of its electrical resistance in an externally-applied magnetic field. In these, a magnetic field can adjust the resistance by orders of magnitude.

Being a transport property magnetoresistance involves the electrons at the Fermi level. In itinerant ferromagnets these are the same electrons which are spin-split and responsible for the magnetism. Magnetoresistance arises due to a small difference in the scattering probabilities for spin-up and spin-down electrons.

In the bulk spin field-effect transistor, the ferromagnetic source or drain act as electrical contacts to the channel when the transistor is working in its on-state, and they work as blocking contacts for leakage current between the source and drain when the transistor is in its off-state.

Magnetometers are widely used for measuring the Earth’s magnetic field, in geophysical surveys, to detect magnetic anomalies of various types, and to determine the dipole moment of magnetic materials. In an aircraft’s attitude and heading reference system, they are commonly used as a heading reference.

Anisotropic MR is a phenomenon that occurs in ferromagnets in which the resistivity depends on the angle between the current and magnetization directions. Figure 52 shows the experimental results obtained for the change in resistivity of Ni when a magnetic field is applied parallel and perpendicular to the current direction.

Anisotropic magnetoresistance (AMR) based sensors are made of thin film (typically, 50 nm) strips of permalloy Anisotropic MR is a phenomenon that occurs in ferromagnets in which the resistivity depends on the angle between the current and magnetization directions.

Anisotropic magnetoresistance (AMR) based sensors are made of thin film (typically, 50 nm) strips of permalloy as shown in Fig. 3. The resistance changes about 2% with the magnetic field due to the spin-dependent scattering. The sensing direction is in the film plane, perpendicular to the strip axis.

Examples ofmetals displaying this behavior are Bi, Sb, W, and Mo. iii)Metals that contain Fermi surfaces with open orbits in some crystallographic directions will exhibit large magnetoresistance for fields applied in those directions, whereas the resistance will saturate in otherdirections, where the orbits are closed.