What is Magneto-resistance?

Magneto-resistance refers to the change in the electrical resistance of a material when subjected to a magnetic field. This phenomenon was first observed by William Thomson in 1856, but it was not until the 1980s that it was utilized in a range of scientific and technological applications.

Magneto-resistance occurs due to the interaction between the magnetic moments of the electrons in a material and an external magnetic field. When the magnetic moments of the electrons align with the external magnetic field, the resistance of the material decreases, and when they are anti-aligned, the resistance increases. This effect is used in a range of scientific and technological applications, including magnetic storage devices and magnetic field sensors.

Types of Magneto-resistance

There are two main types of magneto-resistance: giant magneto-resistance (GMR) and anisotropic magneto-resistance (AMR). GMR was discovered in the late 1980s and is a large effect that occurs in thin film structures that are composed of alternating ferromagnetic and non-magnetic layers. The GMR effect has revolutionized magnetic data storage, enabling the creation of higher-density and higher-capacity hard disk drives.

AMR, on the other hand, is a smaller effect that occurs in single ferromagnetic films or granular magnetic materials. The AMR effect is used in magnetic field sensors, such as compasses and magnetometers, which are used in navigation, geology, and mineral exploration. Both types of magneto-resistance have important technological applications and continue to be an active area of research.

Applications of Magneto-resistance

Magneto-resistance is used in a variety of applications, including magnetic field sensing, magnetic memory, and spintronics. Magnetic field sensors based on magneto-resistance are used in a wide range of technologies, including compasses, magnetometers, and MRI machines. Magneto-resistive random-access memory (MRAM) is a type of non-volatile memory that uses magneto-resistance to store data, and it has the potential to become a major competitor to flash memory.

Magneto-resistance is also used in the field of spintronics, which is a branch of electronics that utilizes the spin of electrons (rather than their charge) to transmit and process information. Spintronics has the potential to revolutionize the computing industry, and magneto-resistance is a key component of many spintronic devices.

Example of Magneto-resistance in Action

One example of magneto-resistance in action is the use of GMR in hard disk drives. In a hard disk drive, data is stored on a spinning disk that is coated with a ferromagnetic material. The data is read and written by a magnetic read/write head, which is composed of a tiny GMR sensor. The GMR sensor is able to detect the small changes in magnetic field that correspond to the data stored on the disk, allowing the read/write head to accurately read and write data at high speeds.

In conclusion, magneto-resistance is a fascinating and useful phenomenon that has revolutionized many areas of technology, including magnetic field sensing, magnetic memory, and spintronics. As research in this field continues, it is likely that we will discover even more exciting applications for magneto-resistance in the future.