ITLApplied  Computational Mathematics Division
ACMD Seminar Series
Attractive Image NIST

Magnetization Dynamics and Random Matrices

Robert McMichael
Metallury Division, Material Science Engineering Laboratory, NIST

Tuesday, January 28, 2003 15:00-16:00,
Room 145, NIST North (820)
Tuesday, January 28, 2003 13:00-14:00,
Room 4550

Abstract: One interesting consequence of the link between the magnetic moment and the spin angular momentum of electrons is that the magnetization precesses around the effective field in a way that is analogous to the precession of a top in the gravitational field. Typical precession frequencies are in the GHz range. Damping processes allow the magnetization to come to equilibrium in a few nanoseconds, a time that is becoming slow relative to data rates in disk drives, magnetic memory chips and sensors. Ferromagnetic resonance experiments use the width of the peak in susceptibility at the magnetization precession frequency to measure magnetization damping. These measurements are generally clouded by the presence of material inhomogeneities that broaden the ferromagnetic resonance lines. In this talk, I will give an introduction to ferromagnetic resonance and three models of the added line width due to inhomogeneities: one that ignores magnetic interactions, one that handles weak inhomogeneities while accounting for interactions, and a new model that links the two older models. This new model requires finding the eigenvalues and eigenmodes of a Hermitian matrix with Fourier components of the random inhomogeneity in the off-diagonal terms. Finally, I will touch on the possible relationships between this work and random matrix theory and localization theory.
Contact: M. J. Donahue

Note: Visitors from outside NIST must contact Robin Bickel; (301) 975-3668; at least 24 hours in advance.

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