Spin-torque microwave detector with out-of-plane precessing magnetic moment

Operation of a spin-torque microwave detector (STMD) in a weak perpendicular bias magnetic field has been studied theoretically. It is shown that in this geometry a novel dynamical regime of STMD operation, characterized by large-angle out-of-plane magnetization precession, can be realized. The excitation of the large-angle precession has threshold character and is possible only for input microwave currents exceeding a certain frequency-dependent critical value. The output voltage of an STMD increases with the frequency of the input signal but is virtually independent of its power. An STMD working in the regime of large-amplitude out-of-plane precession functions as a non-resonant threshold detector of low frequency microwave signals, due to the large nonlinear shift of its operating frequency. Therefore, it is particularly suitable for applications in microwave energy harvesting.