107,033 research outputs found
Layer-resolved imaging of domain wall interactions in magnetic tunnel junction-like trilayers
We have performed a layer-resolved, microscopic study of interactions between
domain walls in two magnetic layers separated by a non-magnetic one, using
high-resolution x-ray photoemission electron microscopy. Domain walls in the
hard magnetic Co layer of a Co/Al2O3/FeNi trilayer with in-plane uniaxial
anisotropy strongly modify the local magnetization direction in the soft
magnetic FeNi layer. The stray fields associated to the domain walls lead to an
antiparallel coupling between the local Co and FeNi moments. For domain walls
parallel to the easy magnetization axis this interaction is limited to the
domain wall region itself. For strongly charged (head-on or tail-to-tail)
walls, the antiparallel coupling dominates the interaction over radial
distances up to several micrometers from the centre of the domain wall.Comment: Published version, J. Phys.: Condens. Matter 19, 476204 (2007
Domain walls in helical magnets
The structure of domain walls determines to a large extent the properties of
magnetic materials, in particular their hardness and switching behavior, it
represents an essential ingredient of spintronics. Common domain walls are of
Bloch and Neel types in which the magnetization rotates around a fixed axis,
giving rise to a one-dimensional magnetization profile. Domain walls in helical
magnets, most relevant in multiferroics, were never studied systematically.
Here we show that domain walls in helical magnets are fundamentally different
from Bloch and Neel walls. They are generically characterized by a
two-dimensional pattern formed by a regular lattice of vortex singularities. In
conical phases vortices carry Berry phase flux giving rise to the anomalous
Hall effect. In multiferroics vortices are charged, allowing to manipulate
magnetic domain walls by electric fields. Our theory allows the interpretation
of magnetic textures observed in helical magnetic structures
Velocity enhancement by synchronization of magnetic domain walls
Magnetic domain walls are objects whose dynamics is inseparably connected to
their structure. In this work we investigate magnetic bilayers, which are
engineered such that a coupled pair of domain walls, one in each layer, is
stabilized by a cooperation of Dzyaloshinskii-Moriya interaction and
flux-closing mechanism. The dipolar field mediating the interaction between the
two domain walls, links not only their position but also their structure. We
show that this link has a direct impact on their magnetic field induced
dynamics. We demonstrate that in such a system the coupling leads to an
increased domain wall velocity with respect to single domain walls. Since the
domain wall dynamics is observed in a precessional regime, the dynamics
involves the synchronization between the two walls, to preserve the flux
closure during motion. Properties of these coupled oscillating walls can be
tuned by an additional in-plane magnetic field enabling a rich variety of
states, from perfect synchronization to complete detuning
Dynamical Generation of the Primordial Magnetic Field by Ferromagnetic Domain Walls
The spontaneous generation of uniform magnetic condensate in gives
rise to ferromagnetic domain walls at the electroweak phase transition. These
ferromagnetic domain walls are caracterized by vanishing effective surface
energy density avoiding, thus, the domain wall problem. Moreover we find that
the domain walls generate a magnetic field at the
electroweak scale which account for the seed field in the so called dynamo
mechanism for the cosmological primordial magnetic field. We find that the
annihilation processes of walls with size could release an
energy of order indicating the invisible ferromagnetic walls as
possible compact sources of Gamma Ray Bursts.Comment: LaTeX, 8 pages, 1 figur
Triplet superconductivity and proximity effect induced by Bloch and N\'{e}el domain walls
Noncollinear magnetic interfaces introduced in superconductor
(SC)/ferromagnet/SC heterostructures allow for spin-flipping processes and are
able to generate equal-spin spin-triplet pairing correlations within the
ferromagnetic region. This leads to the occurrence of the so-called long-range
proximity effect. Particular examples of noncollinear magnetic interfaces
include Bloch and N\'{e}el domain walls. Here, we present results for
heterostructures containing Bloch and N\'{e}el domain walls based on
self-consistent solutions of the spin-dependent Bogoliubovde Gennes
equations in the clean limit. In particular, we investigate the thickness
dependence of Bloch and N\'{e}el domain walls on induced spin-triplet pairing
correlations and compare with other experimental and theoretical results,
including conical magnetic layers as noncollinear magnetic interfaces. It is
shown that both, Bloch and N\'{e}el domain walls lead to the generation of
unequal-spin spin-triplet pairing correlations of similar strength as for
conical magnetic layers. However, for the particular heterostructure geometries
investigated, only Bloch domain walls lead to the generation of equal-spin
spin-triplet pairing correlations. They are stronger than those generated by an
equivalent thickness of conical magnetic layers. In order for N\'{e}el domain
walls to induce equal-spin spin-triplet pairing correlations, they have to be
oriented such that the noncollinearity appears within the plane parallel to the
interface region.Comment: 11 pages, 4 figure
Influence of magnetic field and ferromagnetic film thickness on domain pattern transfer in multiferroic heterostructures
Domains in BaTiO induces a regular modulation of uniaxial magnetic
anisotropy in CoFeB via an inverse magnetostriction effect. As a result, the
domain structures of the CoFeB wedge film and BaTiO substrate correlate
fully and straight ferroelectric domain boundaries in BaTiO pin magnetic
domain walls in CoFeB. We use x-ray photoemission electron microscopy and
magneto-optical Kerr effect microscopy to characterize the spin structure of
the pinned domain walls. In a rotating magnetic field, abrupt and reversible
transitions between two domain wall types occur, namely, narrow walls where the
magnetization vectors align head-to-tail and much broader walls with
alternating head-to-head and tail-to-tail magnetization configurations. We
characterize variations of the domain wall spin structure as a function of
magnetic field strength and CoFeB film thickness and compare the experimental
results with micromagnetic simulations.Comment: 5 pages, 5 figure
Field Tuning of Ferromagnetic Domain Walls on Elastically Coupled Ferroelectric Domain Boundaries
We report on the evolution of ferromagnetic domain walls during magnetization
reversal in elastically coupled ferromagnetic-ferroelectric heterostructures.
Using optical polarization microscopy and micromagnetic simulations, we
demonstrate that the spin rotation and width of ferromagnetic domain walls can
be accurately controlled by the strength of the applied magnetic field if the
ferromagnetic walls are pinned onto 90 degrees ferroelectric domain boundaries.
Moreover, reversible switching between magnetically charged and uncharged
domain walls is initiated by magnetic field rotation. Switching between both
wall types reverses the wall chirality and abruptly changes the width of the
ferromagnetic domain walls by up to 1000%.Comment: 5 pages, 5 figure
Intrinsic Domain Wall Resistance in Ferromagnetic Semiconductors
Transport through zincblende magnetic semiconductors with magnetic domain
walls is studied theoretically. We show that these magnetic domain walls have
an intrinsic resistance due to the spin-orbit interaction. The intrinsic
resistance is independent of the domain wall shape and width when the latter is
larger than the Fermi wavelength. For typical parameters, the intrinsic domain
wall resistance is comparable to the Sharvin resistance and should be
experimentally measurable.Comment: Final versio
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