2,651 research outputs found
Rashba Torque Driven Domain Wall Motion in Magnetic Helices
Manipulation of the domain wall propagation in magnetic wires is a key
practical task for a number of devices including racetrack memory and magnetic
logic. Recently, curvilinear effects emerged as an efficient mean to impact
substantially the statics and dynamics of magnetic textures. Here, we
demonstrate that the curvilinear form of the exchange interaction of a magnetic
helix results in an effective anisotropy term and Dzyaloshinskii--Moriya
interaction with a complete set of Lifshitz invariants for a one-dimensional
system. In contrast to their planar counterparts, the geometrically induced
modifications of the static magnetic texture of the domain walls in magnetic
helices offer unconventional means to control the wall dynamics relying on
spin-orbit Rashba torque. The chiral symmetry breaking due to the
Dzyaloshinskii-Moriya interaction leads to the opposite directions of the
domain wall motion in left- or right-handed helices. Furthermore, for the
magnetic helices, the emergent effective anisotropy term and
Dzyaloshinskii-Moriya interaction can be attributed to the clear geometrical
parameters like curvature and torsion offering intuitive understanding of the
complex curvilinear effects in magnetism
Curvature induced magnonic crystal in nanowires
A new type of magnonic crystals, curvature induced ones, is realized in
ferromagnetic nanowires with periodically deformed shape. A magnon band
structure of such crystal is fully determined by its curvature: the developed
theory is well confirmed by simulations. An application to nanoscale spintronic
devises with the geometrically tunable parameters is proposed, namely, to
filter elements.Comment: 21 pages, 6 figures, for submission to SciPos
Liquid crystal anchoring transitions on aligning substrates processed by plasma beam
We observe a sequence of the anchoring transitions in nematic liquid crystals
(NLC) sandwiched between the hydrophobic polyimide substrates treated with the
plasma beam. There is a pronounced continuous transition from homeotropic to
low tilted (nearly planar) alignment with the easy axis parallel to the
incidence plane of the plasma beam (the zenithal transition) that takes place
as the exposure dose increases. In NLC with positive dielectric anisotropy, a
further increase in the exposure dose results in in-plane reorientation of the
easy axis by 90 degrees (the azimuthal transition). This transition occurs
through the two-fold degenerated alignment characteristic for the second order
anchoring transitions. In contrast to critical behavior of anchoring, the
contact angle of NLC and water on the treated substrates monotonically declines
with the exposure dose. It follows that the surface concentration of
hydrophobic chains decreases continuously. The anchoring transitions under
consideration are qualitatively interpreted by using a simple phenomenological
model of competing easy axes which is studied by analyzing anchoring diagrams
of the generalized polar and non-polar anchoring models.Comment: revtex4, 18 pages, 10 figure
- …