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)

Current driven spin wave instability Y. Ji, C.L. Chien Cond-mat/0210116 M. Tsoi et al. E.B. Myers et al.,Science 285, 867 (1999).

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:

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

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

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

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

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)

Conclusions Spin wave spectrum of current driven ferromagnetic metals Enhanced Damping Email: joaquin@physics.utexas.edu

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