spintransfertorquen

Spin transfer torque is a phenomenon in spintronics where the spin angular momentum of conduction electrons is used to switch the magnetization of a ferromagnetic material. This occurs when a spin-polarized current flows through a magnetic multilayer structure. The electrons in the current carry a net spin polarization, meaning more electrons are aligned with a particular spin direction than the opposite. As these electrons pass through a magnetic layer, they interact with the local magnetization. This interaction can transfer spin angular momentum from the electrons to the magnetic layer. If the spin-polarized current is sufficiently high, this transferred angular momentum can be enough to overcome the magnetic anisotropy of the layer and cause its magnetization to flip.

This effect is typically observed in magnetic tunnel junctions (MTJs) or spin valves, which consist of alternating ferromagnetic and non-magnetic layers. The efficiency of spin transfer torque depends on factors such as the degree of spin polarization of the current, the interface transparency, and the magnetic properties of the layers involved. Spin transfer torque has become a key mechanism for writing data in magnetic random-access memory (MRAM) devices. Its ability to switch magnetization without requiring an external magnetic field offers advantages in terms of power consumption and device scalability. Research continues to explore ways to enhance the efficiency of spin transfer torque and develop new applications in data storage and processing.