Spin-torque ac impedance in magnetic tunnel junctions

Subjecting a magnetic tunnel junction (MTJ) to a spin-transfer torque and/or electric voltage-induced magnetic anisotropy induces magnetic precession, which can reciprocally pump current through the circuit. This results in an ac impedance, which is sensitive to the magnetic field applied to the MTJ. Measurement of this impedance can be used to characterize the nature of the coupling between the magnetic free layer and the electric input as well as a readout of the magnetic configuration of the MTJ.