Magnetic nanostructure control via spin torque

Spin is a genuine quantum degree of freedom that does not have classical correspondence. In ferromagnets, the spin-spin exchange interaction can have sizable magnitude (~ eV) and thus magnetic ordering can be in principle manipulated by using this exchange interaction. For instance, when spin-polarized currents are injected into ferromagnets and if the spin polarization direction of the currents differs from the magnetization direction of the ferromagnet, the exchange interaction induces magnetization dynamics. Spin transfer torque refers to torque that acts on ferromagnets due to the injected spin-polarized currents. In this talk, I will review basic concept of the spin transfer torque and also recent efforts to utilize this for device applications.