Magnonic momentum transfer force on domain walls confined in space

Momentum transfer from incoming magnons to a Bloch domain wall is calculated using one dimensional continuum micromagnetic analysis. Due to the confinement of the wall in space, the dispersion relation of magnons is different from that of a single domain. This mismatch of dispersion relations can result in reflection of magnons upon incidence on the domain wall, whose direct consequence is a transfer of momentum between magnons and the domain wall. The corresponding counteraction force exerted on the wall can be used for the control of domain wall motion through magnonic linear momentum transfer, in analogy with the spin transfer torque induced by magnonic angular momentum transfer.Comment: 5 pages, 3 figure, published versio

Magnonic band structure of domain wall magnonic crystals

Magnonic crystals are prototype magnetic metamaterials designed for the control of spin wave propagation. Conventional magnonic crystals are composed of single domain elements. If magnetization textures, such as domain walls, vortices and skyrmions, are included in the building blocks of magnonic crystals, additional degrees of freedom over the control of the magnonic band structure can be achieved. We theoretically investigate the influence of domain walls on the spin wave propagation and the corresponding magnonic band structure. It is found that the rotation of magnetization inside a domain wall introduces a geometric vector potential for the spin wave excitation. The corresponding Berry phase has quantized value $4 n_w \pi$, where $n_w$ is the winding number of the domain wall. Due to the topological vector potential, the magnonic band structure of magnonic crystals with domain walls as comprising elements differs significantly from an identical magnonic crystal composed of only magnetic domains. This difference can be utilized to realize dynamic reconfiguration of magnonic band structure by a sole nucleation or annihilation of domain walls in magnonic crystals.Comment: 21 pages, 9 figure

Transmission of doughnut light through a bull's eye structure

We experimentally investigate the extraordinary optical transmission of doughnut light through a bull's eye structure. Since the intensity is vanished in the center of the beam, almost all the energy reaches the circular corrugations (not on the hole), excite surface plasmons which propagate through the hole and reradiate photons. The transmitted energy is about 57 times of the input energy on the hole area. It is also interesting that the transmitted light has a similar spatial shape with the input light although the diameter of the hole is much smaller than the wavelength of light.Comment: 3 pages,4 figure