THESIS
2013
xv, 151 pages : illustrations ; 30 cm
Abstract
This thesis is devoted to the study of the nonlinear dynamics of the Landau-Lifshitz-Gilbert
equation which universally governs the magnetization dynamics. It consists of two distinct
components. Firstly, self-sustained current oscillations observed in spin-blockaded double
quantum dots are explained as a consequence of periodic motions (along a limit cycle) of the
magnetization generated by the dynamically polarized nuclear spins under an external magnetic
field and a spin-transfer torque. Based on the Landau-Lifshitz-Gilbert equation, it is shown that
a sequence of semi-stable limit cycle, Hopf and homoclinic bifurcations occurs as the external
field is tuned. The divergent period near the homoclinic bifurcation explains well why the period
in experiments can be many orders of...[
Read more ]
This thesis is devoted to the study of the nonlinear dynamics of the Landau-Lifshitz-Gilbert
equation which universally governs the magnetization dynamics. It consists of two distinct
components. Firstly, self-sustained current oscillations observed in spin-blockaded double
quantum dots are explained as a consequence of periodic motions (along a limit cycle) of the
magnetization generated by the dynamically polarized nuclear spins under an external magnetic
field and a spin-transfer torque. Based on the Landau-Lifshitz-Gilbert equation, it is shown that
a sequence of semi-stable limit cycle, Hopf and homoclinic bifurcations occurs as the external
field is tuned. The divergent period near the homoclinic bifurcation explains well why the period
in experiments can be many orders of magnitude longer than all microscopic time scales.
Secondly, the stability of the well-known Walker propagating domain-wall solution of the Landau-
Lifshitz-Gilbert equation is analytically investigated. Surprisingly, a propagating domain-wall
is always dressed with spin-waves so that the Walker rigid-body propagating domain-wall
mode does not occur in reality. In the low field region only stern spin-waves are emitted while
both stern and bow waves are generated under high fields. In a high enough field, but below the
Walker breakdown field, the Walker solution can be convectively/absolutely unstable if the
transverse magnetic anisotropy is larger than a critical value, corresponding to a significant
modification of the domain-wall profile and domain-wall propagating speed.
Post a Comment