| Summary: | 博士 === 國立清華大學 === 物理學系 === 85 === The generalized Slonczewski equations have been applied to study
the influenceof the field normal to the anisotropy axis on the
Walker critical field, critical velocity and the maximum
velocity of the steady-state domain wall motion. It is shown
that the maximum value of the steady-state velocity of the
domain wall is the Schlomann limiting velocity which is drive
field dependent. The dependences of the Walker critical field
and velocity as well as Schlomann limiting velocity on the field
normal to the anisotropy axis have been obtained. The new
equations take into account the relaxational dynamics of
magnetization modulus first introduced into the Landau-Lifshitz
equation by Bar'yakhtar. In the derivation of linear mobility, a
new expression of a relaxation parameter is obtained. It
reaveals a relation between ferromagnetic resonance(FMR) line
width and the relaxation parameter obtained from mobility
measurement. Based on this relation, it is found that the
nonconservation of magnetization modulus gives rise to a larger
contribution to the domain wall drag in ferromagnets with a
narrower FMR line width than in ones with a wider line width.
The description of the steady state domain wall motion in the
traditional Landau-Lifshitz-Gilbert equation may give
essentially the same dependency upon the drive field and
transverse field provided if the phenomenological relaxation
constant is deduced directly from experimental data on the
domain wall mobility, instead of from a ferromagnet with a wide
resonance line width. It is also found that the drag force due
to nonconservation of magnetization modulus is enhanced by drive
field but depressed by transeverse field.
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