The performance characteristics of a microwave vortex nanogenerator
Keywords:
spin-transfer vortex nanooscillator, vortex dynamics, power optimizationAbstract
Magnetic vortices induced in magnetic nanostructures by a spin-polarized current that flows through them as a result of the spin transfer effect (a so-called “spin-transfer torque”) are of significant interest for certain applications. In particular, fundamentally new compact microwave range generators with a widely adjusted frequency called spin-transfer nanooscillators (STNOs) can be implemented on the basis of vortex magnetization dynamics in magnetic nanostructures. In contrast to homogeneous STNOs, vortex STNOs have significant advantages: a smaller spectral line width (about 1 MHz at frequencies of up 1 GHz), larger output power (about 1 μW), and the absence of an external magnetic field. However, for such generators could be used for practical applications, it is necessary to reduce the STNO spectral line width. One of possible ways in which the spectral line width of oscillations generated by a vortex STNO can be reduced consists in using its external synchronization by a harmonic high-frequency current or magnetic field. Reduced equations for slowly varying amplitude and phase of a vortex STNO synchronized from an external harmonic source are derived based on Thiel’s equation for a vortex core. The STNO resistive equivalent circuit was constructed, from which the STNO performance characteristics were obtained, and its optimal parameters were found at which the maximum output power on the load is achieved. The STNO frequency adjustment range has been determined using the developed model.
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