Time domain measurement of phase noise in a spin torque oscillator

Keller, Mark W.
Kos, A. B.
Silva, T. J.
Rippard, W. H.
Pufall, M. R.
Description
We measure oscillator phase from the zero crossings of the voltage vs. time waveform of a spin torque nanocontact oscillating in a vortex mode. The power spectrum of the phase noise varies with Fourier frequency $f$ as $1/f^2$, consistent with frequency fluctuations driven by a thermal source. The linewidth implied by phase noise alone is about 70 % of that measured using a spectrum analyzer. A phase-locked loop reduces the phase noise for frequencies within its 3 MHz bandwidth.
Comment: 6 pages, 5 figures, supplementary material. Submitted to {Appl. Phys. Lett.}
Keywords
Condensed Matter - Mesoscale and Nanoscale Physics