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Weighting a Domain Wall. Journal Club February 15 2005 Current-Induced resonance and mass determination of a single magnetic domain wall, Nature 432 , 203 (2004) Elji Saitoh, Hideki Miyajima, Takehiro Yamaoka and Gen Tatara. Motivation.
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Weighting a Domain Wall Journal Club February 15 2005 Current-Induced resonance and mass determination of a single magnetic domain wall, Nature 432, 203 (2004) Elji Saitoh, Hideki Miyajima, Takehiro Yamaoka and Gen Tatara
Motivation • Fundammental Phyics: interaction between currents and Domain Walls • Great Experiment • Opens INTERESTING QUESTIONS (Related to our future work) • Related to some of my recent work: • JFR, M. Braun, A.S. Núñez, AH. MacDonald Phys. Rev. B 2004 • J. J. Palacios, D. Jacob, JFR, cond-mat/2004 • L. Brey, C. Tejedor, JFR, APL 2004
What is a Domain Wall (DW) Ferromagnetic Ground State. Good for local EXCHANGE. BAD for Magnetostatics Ferromagnetic DOMAIN EXCHANGE ok except in the WALL GOOD for Magnetostatics DOMAIN and GROUND STATE ARETOPOLOGICALLY DIFFERENT DOMAIN WALL
Thin DW DW: Thick or Thin COMPETION between EXCHANGE and anisotropic interactions Exchange favors thick DW Anis. Int. Favors thin DW Thick DW
Justification of x y Clockwise Anti- Clockwise
LATER: • Why a DW can be considered a particle with mass? • What is a “magnetic charge”?
MagneticForceMicroscopy Resistance vs a.c. frequency
mDW=(6.55+- 0.06 ) 10-23 Kg , Is: spin current f: frequency m: DW mass, : DW relaxation time n: conduction electron density RDW: DW resistance I: total current
DW: From Field to Particle M,x, F(x) • PAPERS: • S. Takagi and G. Tatara, Phys. Rev. B 54, 9920 (1996). • H-B. Braun and D. Loss, Phys. Rev. B 53, 3237 (1996); • P. C. E. Stamp, Phys. Rev. Lett. 66, 2802 (1991). • E. M. Chudnovsky, O. Iglesias, and P. C. E. Stamp, Phys. Rev. B 46, 5392 (1992). .
DW: From Field to Particle Classical Lagrangian of a Field
DW “mass” “Magnetic Charge” Magnetic Energy
Magnetostatics “Magnetic Charge” Polarization Charge
DW theory EXCHANGE