Spin-torque microwave detectors: Fundamentals and applications

It is known that the spin-transfer torque (STT) effect in magnetic multilayers, theoretically predicted in [1, 2] and experimentally observed in [3-13], provides a new method of manipulation of magnetization in nanoscale objects [14]: magnetization switching [3, 4] and generation of microwave oscillations under the action of a dc electric current [5-11]. According to the STT effect bias dc current traversing magnetic multilayers can transfer angular magnetic moments from one layer to another, which can give rise to the microwave dynamics of magnetization in the layer [1-11]. However, it is clear that an inverse effect is also possible. This inverse effect leads to the so-called spin-torque diode effect [12-13], first originally observed experimentally in 2005. It can be used for the development of practical microwave detectors, so called spin-torque microwave detectors (STMD), and also for quantitatively measuring STT [15, 16].