Direct-current induced dynamics in Co90 Fe10/Ni80 Fe20 point contacts.
We have directly measured coherent high-frequency magnetization dynamics in ferromagnetic films induced by a spin-polarized dc current. The precession frequency can be tuned over a range of several gigahertz by varying the applied current. The frequencies of excitation also vary with applied field, resulting in a microwave oscillator that can be tuned from below 5 to above 40 GHz. This novel method of inducing high-frequency dynamics yields oscillations having quality factors from 200 to 800. We compare our results with those from single-domain simulations of current-induced dynamics.
Rippard
W H
WH
National Institute of Standards and Technology, Boulder, Colorado 80305, USA.
Pufall
M R
MR
Kaka
S
S
Russek
S E
SE
Silva
T J
TJ