A Magnetic Tunnel Junction (MTJ) is a device that consists of two ferromagnetic layers separated by a thin insulating barrier. When a voltage is applied, electrons can tunnel through the insulator, allowing the device to switch between different magnetic states. This property makes MTJs useful in various applications, including data storage and memory devices. MTJs are a key component in technologies like spintronics, which exploits the spin of electrons in addition to their charge. They are also used in MRAM (Magnetoresistive Random Access Memory), offering non-volatile memory solutions that retain data even when power is turned off.