Decoherence, Mode Hopping, and Mode Coupling in Spin Torque Oscillators
Artikel i vetenskaplig tidskrift, 2013

Spin torque oscillators (STOs) often exhibit multiple modes, leading to complex behavior. One example is mode hopping between different eigenmodes of a magnetic tunnel junction (MTJ) STO. This mode hopping is a strong function of current and angle between the magnetization in the free and fixed layers, and away from anti-parallel configuration, mode hopping can be the dominant decoherence process. Another example is the linewidth of a nanocontact STO that can be a complex non-monotonic function of temperature in regions where two or more modes are excited by the oscillators. These phenomena require a generalization of the single-mode nonlinear STO theory to include mode coupling. We derive equations describing the slow time evolution of the coupled system and show they describe a dynamically driven system, similar to other systems that exhibit mode hopping in the presence of thermal fluctuations. In our description, mode coupling also leads to additional coupling between power and phase fluctuations, which can in certain limited cases lead to longer relaxation times for power fluctuations, and consequently to larger linewidths through the nonlinear frequency shift.

microwave oscillators

GENERATION

EXCITATION

tunneling

DRIVEN

WAVES

spin polarized transport

MAGNETIC MULTILAYERS

NANO-OSCILLATORS

POLARIZED CURRENT

MODULATION

spin valves

Magnetoresistive devices

Författare

O. G. Heinonen

Pranaba Muduli Kishor

Göteborgs universitet

Ezio Iacocca

Göteborgs universitet

Johan Åkerman

Göteborgs universitet

IEEE Transactions on Magnetics

0018-9464 (ISSN)

Vol. 49 7 4398-4404

Ämneskategorier

Fysik

DOI

10.1109/tmag.2013.2242866