Vortex Domain Walls in Helical Magnets

Collective magnetism at multiferroic vortex domain walls.

Cross-coupled phenomena of multiferroic domains and domain walls are of fundamental scientific and technological interest. Using cryogenic magnetic force microscopy, we find alternating net magnetic moments at ferroelectric domain walls around vortex cores in multiferroic hexagonal ErMnO(3), which correlate with each other throughout the entire vortex network. This collective nature of domain w...

Domain wall mobility in nanowires: Transverse versus vortex walls

The motion of domain walls in ferromagnetic, cylindrical nanowires is investigated numerically by solving the Landau-Lifshitz-Gilbert equation for a classical spin model in which energy contributions from exchange, crystalline anisotropy, dipole-dipole interaction, and a driving magnetic field are considered. Depending on the diameter, either transverse domain walls or vortex walls are found. T...

Structure of macrodomain walls in polytwinned magnets

Dynamical magnetoelectric coupling in helical magnets.

We develop a theory of collective mode dynamics in the helical magnets coupled to electric polarization via spin-orbit interaction. The low-lying modes associated with the ferroelectricity are not the transverse optical phonons, but are the spin waves hybridized with the electric polarization. This hybridization leads to the Drude-like dielectric function epsilon(omega) in the limit of zero mag...

Ground State Structure, Domain Walls, and External Field Response in Random Magnets

The ground state structure and domain walls in Ising-like magnets with quenched randomness are studied at zero temperature. The methods employed are exact ground state calculations using graph-theoretical optimization and extreme statistics arguments. The elastic manifolds, i.e., domain walls, with random-bond disorder are investigated with two different types of periodicity. The first type of ...