Abstract
Spin-valve based nanojunctions incorporating Co∫Ni multilayers with perpendicular anisotropy were used to study spin-torque driven ferromagnetic resonance (ST-FMR) in a nonlinear regime. Perpendicular field swept resonance lines were measured under a large amplitude microwave current excitation, which produces a large angle precession of the Co∫Ni layer magnetization. With increasing rf power the resonance lines broaden and become asymmetric, with their peak shifting to lower applied field. A nonhysteretic step jump in ST-FMR voltage signal was also observed at high powers. The results are analyzed in terms of the foldover effect of a forced nonlinear oscillator and compared to macrospin simulations. The ST-FMR nonhysteretic step response may have applications in frequency and amplitude tunable nanoscale field sensors.
Original language | English (US) |
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Article number | 172513 |
Journal | Applied Physics Letters |
Volume | 95 |
Issue number | 17 |
DOIs | |
State | Published - 2009 |
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)