421 research outputs found
X-ray magnetic linear dichroism as a probe for non-collinear magnetic state in ferrimagnetic single layer exchange bias systems
Ferrimagnetic alloys are extensively studied for their unique magnetic
properties leading to possible applications in perpendicular magnetic
recording, due to their deterministic ultrafast switching and heat assisted
magnetic recording capabilities. On a prototype ferrimagnetic alloy we
demonstrate fascinating properties that occur close to a critical temperature
where the magnetization is vanishing, just as in an antiferromagnet. From the
X-ray magnetic circular dichroism measurements, an anomalous 'wing shape'
hysteresis loop is observed slightly above the compensation temperature. This
bears the characteristics of an intrinsic exchange bias effect, referred to as
atomic exchange bias. We further exploit the X-ray magnetic linear dichroism
(XMLD) contrast for probing non-collinear states which allows us to
discriminate between two main reversal mechanisms, namely perpendicular domain
wall formation versus spin-flop transition. Ultimately, we analyze the
elemental magnetic moments for the surface and the bulk parts, separately,
which allows to identify in the phase diagram the temperature window where this
effect takes place. Moreover, we suggests that this effect is a general
phenomenon in ferrimagnetic thin films which may also contribue to the
understanding of the mechanism behind the all optical switching effect.Comment: 20 pages, 9 figure
Spin structure relation to phase contrast imaging of isolated magnetic Bloch and Neel skyrmions
Magnetic skyrmions are promising candidates for future storage devices with a
large data density. A great variety of materials have been found that host
skyrmions up to the room-temperature regime. Lorentz microscopy, usually
performed in a transmission electron microscope (TEM), is one of the most
important tools for characterizing skyrmion samples in real space. Using
numerical calculations, this work relates the phase contrast in a TEM to the
actual magnetization profile of an isolated Neel or Bloch skyrmion, the two
most common skyrmion types. Within the framework of the used skyrmion model,
the results are independent of skyrmion size and wall width and scale with
sample thickness for purely magnetic specimens. Simple rules are provided to
extract the actual skyrmion configuration of pure Bloch or Neel skyrmions
without the need of simulations. Furthermore, first differential phase contrast
(DPC) measurements on Neel skyrmions that meet experimental expectations are
presented and showcase the described principles. The work is relevant for
material sciences where it enables the engineering of skyrmion profiles via
convenient characterization.Comment: 6 pages, 3 figure
Resonant elastic X-ray scattering of antiferromagnetic superstructures in EuPtSi
We report resonant elastic X-ray scattering (REXS) of long-range magnetic
order in EuPtSi, combining different scattering geometries with
full linear polarization analysis to unambiguously identify magnetic scattering
contributions. At low temperatures, EuPtSi stabilizes type A
antiferromagnetism featuring various long-wavelength modulations. For magnetic
fields applied in the hard magnetic basal plane, well-defined regimes of
cycloidal, conical, and fan-like superstructures may be distinguished that
encompass a pocket of commensurate type A order without superstructure. For
magnetic field applied along the easy axis, the phase diagram comprises the
cycloidal and conical superstructures only. Highlighting the power of polarized
REXS, our results reveal a combination of magnetic phases that suggest a highly
unusual competition between antiferromagnetic exchange interactions with
Dzyaloshinsky--Moriya spin--orbit coupling of similar strength
Growth and Helicity of Noncentrosymmetric Cu<sub>2</sub>OSeO<sub>3</sub> Crystals
We have grown CuOSeO single crystals with an optimized chemical vapor
transport technique by using SeCl as a transport agent. Our optimized
growth method allows to selectively produce large high quality single crystals.
The method is shown to consistently produce CuOSeO crystals of maximum
size 8 mm x 7 mm x 4 mm with a transport duration of around three weeks. We
found this method, with SeCl as transport agent, more efficient and simple
compared to the commonly used growth techniques reported in literature with HCl
gas as transport agent. The CuOSeO crystals have very high quality and
the absolute structure are fully determined by simple single crystal x-ray
diffraction. We observed both type of crystals with left- and right-handed
chiralities. Our magnetization and ferromagnetic resonance data show the same
magnetic phase diagram as reported earlier
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