Friday, April 15
11 AM
Sumwalt 120A (conference room)

On-line seminar
Prof. Oleg Tchernyshyov
Johns Hopkins University

Dynamics of Bloch domain walls in thin magnetic films

A thin magnetic film with a strong easy-axis anisotropy favoring the
out-of-plane direction breaks up into mesoscopic magnetic domains 
separated by Bloch domain walls.  Depending on magnetic history, these 
domains can form ordered stripes or disordered labyrinthine patterns.  
The physics of these domain walls is strongly influenced by dipolar 
interactions that mediate a long-range interaction between domain walls 
and make the wall tension negative [1].  Here we point out that the 
dominance of the gyrotropic force over the viscous one makes the 
dynamics of Bloch walls rather unusual.  Low-frequency waves on such a 
wall are chiral: the speed of propagation is different for the two 
directions along the wall.  The puzzling star-shaped trajectory of a 
magnetic bubble noted in [2] is a result of superposition of two waves 
with the same wavenumber and different frequencies running in opposite 
directions along the wall that surrounds the bubble.  We point out a 
similarity to the edges of a quantum Hall state.

[1] S. A. Langer, R. E. Goldstein, and D. P. Jackson, Phys. Rev. A 46, 4894 (1992).

[2] C. Moutafis, S. Komineas, and J. A. C. Bland, Phys. Rev. B 79, 224429 (2009).