Dependence of the colored frequency noise in spin torque oscillators on current and magnetic field
Artikel i vetenskaplig tidskrift, 2014

The nano-scale spin torque oscillator (STO) is a compelling device for on-chip, highly tunable microwave frequency signal generation. Currently, one of the most important challenges for the STO is to increase its longer-time frequency stability by decreasing the 1/f frequency noise, but its high level makes even its measurement impossible using the phase noise mode of spectrum analyzers. Here, we present a custom made time-domain measurement system with 150MHz measurement bandwidth making possible the investigation of the variation of the 1/f as well as the white frequency noise in a STO over a large set of operating points covering 18-25GHz. The 1/f level is found to be highly dependent on the oscillation amplitude-frequency non-linearity and the vicinity of unexcited oscillation modes. These findings elucidate the need for a quantitative theoretical treatment of the low-frequency, colored frequency noise in STOs. Based on the results, we suggest that the 1/f frequency noise possibly can be decreased by improving the microstructural quality of the metallic thin films. (C) 2014 AIP Publishing LLC.





A. Eklund

Stefano Bonetti

S. R. Sani

S. M. Mohseni

J. Persson

S. J. Chung

S. A. H. Banuazizi

Ezio Iacocca

Göteborgs universitet

M. Ostling

Johan Åkerman

Göteborgs universitet

B. G. Malm

Applied Physics Letters

0003-6951 (ISSN) 1077-3118 (eISSN)

Vol. 104