979 research outputs found
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
Non-classical properties and algebraic characteristics of negative binomial states in quantized radiation fields
We study the nonclassical properties and algebraic characteristics of the
negative binomial states introduced by Barnett recently. The ladder operator
formalism and displacement operator formalism of the negative binomial states
are found and the algebra involved turns out to be the SU(1,1) Lie algebra via
the generalized Holstein-Primarkoff realization. These states are essentially
Peremolov's SU(1,1) coherent states. We reveal their connection with the
geometric states and find that they are excited geometric states. As
intermediate states, they interpolate between the number states and geometric
states. We also point out that they can be recognized as the nonlinear coherent
states. Their nonclassical properties, such as sub-Poissonian distribution and
squeezing effect are discussed. The quasiprobability distributions in phase
space, namely the Q and Wigner functions, are studied in detail. We also
propose two methods of generation of the negative binomial states.Comment: 17 pages, 5 figures, Accepted in EPJ
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 , where 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
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