4,119 research outputs found
Deconvoluting Reversal Modes in Exchange Biased Nanodots
Ensemble-averaged exchange bias in arrays of Fe/FeF2 nanodots has been
deconvoluted into local, microscopic, bias separately experienced by nanodots
going through different reversal modes. The relative fraction of dots in each
mode can be modified by exchange bias. Single domain dots exhibit a simple loop
shift, while vortex state dots have asymmetric shifts in the vortex nucleation
and annihilation fields, manifesting local incomplete domain walls in these
nanodots as magnetic vortices with tilted cores.Comment: 17 pages, 3 figures. Phys. Rev. B in pres
Stabilization and current-induced motion of antiskyrmion in the presence of anisotropic Dzyaloshinskii-Moriya interaction
Topological defects in magnetism have attracted great attention due to
fundamental research interests and potential novel spintronics applications.
Rich examples of topological defects can be found in nanoscale non-uniform spin
textures, such as monopoles, domain walls, vortices, and skyrmions. Recently,
skyrmions stabilized by the Dzyaloshinskii-Moriya interaction have been studied
extensively. However, the stabilization of antiskyrmions is less
straightforward. Here, using numerical simulations we demonstrate that
antiskyrmions can be a stable spin configuration in the presence of anisotropic
Dzyaloshinskii-Moriya interaction. We find current-driven antiskyrmion motion
that has a transverse component, namely antiskyrmion Hall effect. The
antiskyrmion gyroconstant is opposite to that for skyrmion, which allows the
current-driven propagation of coupled skyrmion-antiskyrmion pairs without
apparent skyrmion Hall effect. The antiskyrmion Hall angle strongly depends on
the current direction, and a zero antiskyrmion Hall angle can be achieved at a
critic current direction. These results open up possibilities to tailor the
spin topology in nanoscale magnetism, which may be useful in the emerging field
of skyrmionics.Comment: 31 pages, 6 figures, to appear in Physical Review
Asymmetric Reversal in Inhomogeneous Magnetic Heterostructures
Asymmetric magnetization reversal is an unusual phenomenon in antiferromagnet
/ ferromagnet (AF/FM) exchange biased bilayers. We investigated this phenomenon
in a simple model system experimentally and by simulation assuming
inhomogeneously distributed interfacial AF moments. The results suggest that
the observed asymmetry originates from the intrinsic broken symmetry of the
system, which results in local incomplete domain walls parallel to the
interface in reversal to negative saturation of the FM. Magneto-optic Kerr
effect unambiguously confirms such an asymmetric reversal and a depth-dependent
FM domain wall in accord with the magnetometry and simulations.Comment: 4 pages, 4 figure
Probing Magnetic Configurations in Co/Cu Multilayered Nanowires
Magnetic configurations in heterostructures are often difficult to probe when
the magnetic entities are buried inside. In this study we have captured
magnetic and magnetoresistance "fingerprints" of Co nanodiscs embedded in Co/Cu
multilayered nanowires using a first-order reversal curve method. In 200nm
diameter nanowires, the magnetic configurations can be tuned by adjusting the
Co nanodisc aspect ratio. Nanowires with the thinnest Co nanodiscs exhibit
single domain behavior, while those with thicker Co reverse via vortex states.
A superposition of giant and anisotropic magnetoresistance is observed, which
corresponds to the different magnetic configurations of the Co nanodiscs.Comment: 14 pages, 3 figure
Chirality control via double vortices in asymmetric Co dots
Reproducible control of the magnetic vortex state in nanomagnets is of
critical importance. We report on chirality control by manipulating the size
and/or thickness of asymmetric Co dots. Below a critical diameter and/or
thickness, chirality control is achieved by the nucleation of single vortex.
Interestingly, above these critical dimensions chirality control is realized by
the nucleation and subsequent coalescence of two vortices, resulting in a
single vortex with the opposite chirality as found in smaller dots.
Micromagnetic simulations and magnetic force microscopy highlight the role of
edge-bound halfvortices in facilitating the coalescence process.Comment: 15 pages, 4 figure
Growth-Induced In-Plane Uniaxial Anisotropy in VO/Ni Films
We report on a strain-induced and temperature dependent uniaxial anisotropy
in VO/Ni hybrid thin films, manifested through the interfacial
strain and sample microstructure, and its consequences on the angular dependent
magnetization reversal. X-ray diffraction and reciprocal space maps identify
the in-plane crystalline axes of the VO; atomic force and scanning
electron microscopy reveal oriented rips in the film microstructure.
Quasi-static magnetometry and dynamic ferromagnetic resonance measurements
identify a uniaxial magnetic easy axis along the rips. Comparison with films
grown on sapphire without rips shows a combined contribution from strain and
microstructure in the VO/Ni films. Magnetization reversal
characteristics captured by angular-dependent first order reversal curve
measurements indicate a strong domain wall pinning along the direction
orthogonal to the rips, inducing an angular-dependent change in the reversal
mechanism. The resultant anisotropy is tunable with temperature and is most
pronounced at room temperature, which is beneficial for potential device
applications
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