Large amplitude microwave emission and reduced nonlinear phase noise in   Co2Fe(Ge0.5Ga0.5) Heusler alloy based pseudo spin valve nanopillars
  We have studied microwave emission from a current-perpendicular-to-plane pseudo spin valve nanopillars with Heusler alloy Co2Fe(Ga0.5Ge0.5) electrodes. Large emission amplitude exceeding 150 nV/Hz^0.5, partly owing to the large magnetoresistance, and narrow generation linewidth below 10 MHz are observed. We also find that the linewidth shows significant dependence on the applied field magnitude and its angle within the film plane. A minimum in the linewidth is observed when the slope of the frequency versus current becomes near zero. This agrees with theoretical prediction that takes into account non-linear phase noise as a source for linewidth broadening. 
Jaivardhan Sinha, Masamitsu Hayashi, Yukiko K. Takahashi, Tomohiro   Taniguchi, Maksim Drapeko, Seiji Mitani and Kazuhiro Hono
cond-mat.mes-hall cond-mat.mtrl-sci