1. Influence of large currents on the magnetization dynamics of ferromagnetic metals
J. Fernandez-Rossier, M. Braun and A. H. MacDonald
Department of Physics, University of Texas at Austin
Current flow:
How does it affect Magnetization dynamics ?
Magnetization controls
current flow (GMR, TMR)
March Meeting 2003, Austin (TX)

2. Current driven spin wave instability
Y. Ji, C.L. Chien Cond-mat/
M. Tsoi et al.
E.B. Myers et al.,Science 285, 867 (1999).

3. Dynamics: Landau-Lifshitz <-> spin waves
Fully polarized s-d model:
Current
Bazaliy, Jones, Zhang.
This work:
Valid for ALL metallic ferromagnets:
Spin Current
Enhanced Spin Wave Damping:

4. Our model Hubbard Model Itinerant d electrons
Partially polarized electrons
Generalize to LDSA

5. Linear combination e-h pairs
Ground state:
Spin split bands
Spin waves. No current q
No current
Spin wave=
Linear combination e-h pairs

6. Spin waves with current
Total current:
Spin current: q
Current

7. Remarks The extra term modifies the off-diagonal terms in the action
Similar term in super-fluids with super-current
Microscopic derivation
Unrelated to Spin Torque

8. Spin Wave Damping q ( m-1) eV) m ( w 2 4 6 8 10 4 2
Spin waves for iron 4 w ( m
eV)
Gilbert Damping 2
Two magnon damping
Two magnon damping 2 4 6 8 10
q ( m-1)

9. Conclusions Spin wave spectrum of current driven ferromagnetic metals
Enhanced Damping

10. Spin waves in the Hubbard model
D.O.S. EF d
Hubbard model:
Partially polarized
itinerant d-electrons