Spintronics
MRAM computer chips use electron spin rather than charge to store bits of data, which enables them to retain information even when electrical power is turned off.
Electron spin is indicated by the fourth quantum number, also known as the Electron Spin Quantum Number and denoted by ms.
Electron spin can be denoted by an arrow pointing up, which is +1/2, or an arrow pointing down, which is −1/2. An electron has a magnetic field due to its spin. When electrons that have opposite spins are put together, there is no net magnetic field because the positive and negative spins cancel each other out. Therefore, the one unpaired electron in the atom will determine the spin.
Although the electron spin is limited to (+½ ) or ( −½ ), certain rules apply when assigning electrons of different spins to fill a sub-shell.
Spin revolutionized the present day memory devices. spin is given a direction, either "up" or "down". Just as the positive or negative values of an electrical charge can be used to encode data as the 0's and 1's of the binary system, so too can the up and down values of spin. Unlike charge–based data storage, however, spin–based storage does not disappear when the electrical current stops. So we can have a non volatile RAM known as MRAM.