Coresonant Enhancement of Spin-Torque Critical Currents in Spin Valves with a Synthetic-Ferrimagnet Free Layer
Abstract
It is experimentally shown that the critical current for onset of spin torque instability in current-perpendicular-to-plane spin valves can be strongly increased using “synthetic-ferrimagnet” free layers of form FM1/Ru/FM2 (FM=ferrromagnet). However, this increase occurs for only one polarity of bias current. A two-macrospin model is shown to reproduce the observations. The model suggests that this phenomenon is related to a polarity-dependent, spin torque-induced coresonance between the two natural dynamic modes of the FM1/FM2 couple. The coresonance condition facilitates energy transfer out of the spin-torque destabilized mode into the other stable mode whose effective damping (or line width) is strongly enhanced by spin torques.
- Publication:
-
Physical Review Letters
- Pub Date:
- December 2008
- DOI:
- 10.1103/PhysRevLett.101.247205
- arXiv:
- arXiv:0808.2015
- Bibcode:
- 2008PhRvL.101x7205S
- Keywords:
-
- 85.70.Kh;
- 85.70.Ay;
- 85.75.Ss;
- Magnetic thin film devices: magnetic heads;
- domain-motion devices etc.;
- Magnetic device characterization design and modeling;
- Magnetic field sensors using spin polarized transport;
- Condensed Matter - Other Condensed Matter
- E-Print:
- 10 pages (manuscript form), with 4 embedded figures. Submitted for publication. Version #2 contains one additional equation (Eq. 4)