MTJs operate based on the principle of quantum tunneling. When a voltage is applied across the junction, electrons can tunnel through the insulating barrier, with the tunneling probability depending on the relative orientation of the magnetizations in the ferromagnetic layers. If the magnetizations are parallel, the tunneling resistance is low, resulting in a high current. Conversely, if the magnetizations are antiparallel, the resistance is high, leading to a low current. This phenomenon is known as Tunnel Magnetoresistance (TMR).
