25 research outputs found
Electrical writing, deleting, reading, and moving of magnetic skyrmioniums in a racetrack device
A magnetic skyrmionium (also called 2-skyrmion) can be understood as a
skyrmion - a topologically non-trivial magnetic whirl - which is situated in
the center of a second skyrmion with reversed magnetization. Here, we propose a
new optoelectrical writing and deleting mechanism for skyrmioniums in thin
films, as well as a reading mechanism based on the topological Hall voltage.
Furthermore, we point out advantages for utilizing skyrmioniums as carriers of
information in comparison to skyrmions with respect to the current-driven
motion. We simulate all four constituents of an operating skyrmionium-based
racetrack storage device: creation, motion, detection and deletion of bits. The
existence of a skyrmionium is thereby interpreted as a '1' and its absence as a
'0' bit.Comment: This is a post-peer-review, pre-copyedit version of an article
published in Scientific Reports. The final authenticated version is available
online at [DOI
Twisting and tweezing the spin wave: on vortices, skyrmions, helical waves, and the magnonic spiral phase plate
Spin waves are the low-energy excitations of magnetically ordered materials.
They are key elements in the stability analysis of the ordered phase and have a
wealth of technological applications. Recently, we showed that spin waves of a
magnetic nanowire may carry a definite amount of orbital angular momentum
components along the propagation direction. This helical, in addition to the
chiral, character of the spin waves is related to the spatial modulations of
the spin wave phase across the wire. It, however, remains a challenge to
generate and control such modes with conventional magnetic fields. Here, we
make the first proposal for a \textit{magnetic} spiral phase plate by
appropriately synthesizing two magnetic materials that have different speeds of
spin waves. It is demonstrated with full-numerical micromagnetic simulations
that despite the complicated structure of demagnetization fields, a homogeneous
spin wave passing through the spiral phase plate attains the required twist and
propagates further with the desired orbital angular momentum. While excitations
from the ordered phase may have a twist, the magnetization itself can be
twisted due to internal fields and forms what is known as a magnetic vortex. We
point out the differences between both types of magnetic phenomena and discuss
their possible interaction.Comment: 6 pages, 5 figure
Risk governance in organizations
Dieses Buch dokumentiert 10 Jahre Risk-Governance-Forschung an der Universität Siegen. In 50 Beiträgen reflektieren Forscher und Praktiker Risk Governance vor dem Hintergrund ihrer eigenen Forschungen und/oder Erfahrungen und geben jeweils einen Entwicklungsimpuls für die Zukunft der Risk Governance. Das Buch zeigt die große Bandbreite und Tiefe des Forschungsgebietes auf und diskutiert Grundannahmen, Implementierungsfragen, die Rolle der Risk Governance als Transformationsmotor, ihre Wirkung in den verschiedenen betrieblichen Funktionen, Entwicklungsperspektiven und den Beitrag der Risk Governance zu einer nachhaltigen Ausrichtung von Unternehmen.This book documents 10 years of risk governance research at the University of Siegen. In 50 contributions, researchers and practitioners reflect on risk governance against the background of their own research and/or experience and provide a development impetus for the future of risk governance. The book shows the wide range and depth of the research field and discusses basic assumptions, implementation issues, the role of risk governance as transformation engine, its impact in the various operational functions, development perspectives, and the contribution of risk governance to a sustainable orientation of companies
Variation in neurosurgical management of traumatic brain injury
Background: Neurosurgical management of traumatic brain injury (TBI) is challenging, with only low-quality evidence. We aimed to explore differences in neurosurgical strategies for TBI across Europe. Methods: A survey was sent to 68 centers participating in the Collaborative European Neurotrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study. The questionnaire contained 21 questions, including the decision when to operate (or not) on traumatic acute subdural hematoma (ASDH) and intracerebral hematoma (ICH), and when to perform a decompressive craniectomy (DC) in raised intracranial pressure (ICP). Results: The survey was completed by 68 centers (100%). On average, 10 neurosurgeons work in each trauma center. In all centers, a neurosurgeon was available within 30Â min. Forty percent of responders reported a thickness or volume threshold for evacuation of an ASDH. Most responders (78%) decide on a primary DC in evacuating an ASDH during the operation, when swelling is present. For ICH, 3% would perform an evacuation directly to prevent secondary deterioration and 66% only in case of clinical deterioration. Most respondents (91%) reported to consider a DC for refractory high ICP. The reported cut-off ICP for DC in refractory high ICP, however, differed: 60% uses 25Â mmHg, 18% 30Â mmHg, and 17% 20Â mmHg. Treatment strategies varied substantially between regions, specifically for the threshold for ASDH surgery and DC for refractory raised ICP. Also within center variation was present: 31% reported variation within the hospital for inserting an ICP monitor and 43% for evacuating mass lesions. Conclusion: Despite a homogeneous organization, considerable practice variation exists of neurosurgical strategies for TBI in Europe. These results provide an incentive for comparative effectiveness research to determine elements of effective neurosurgical care
Twisted magnon beams carrying orbital angular momentum
The magnonic currents promise the opportunity for the energy efficient information processing and communication technologies. Here the authors theoretically show the propagating spin waves that carry orbital angular momentum can be electrically tunable and protected against damping in a cylindrical magnetic insulator waveguide
Rotating edge-field driven processing of chiral spin textures in racetrack devices
Topologically distinct magnetic structures like skyrmions, domain walls, and
the uniformly magnetized state have multiple applications in logic devices,
sensors, and as bits of information. One of the most promising concepts for
applying these bits is the racetrack architecture controlled by electric
currents or magnetic driving fields. In state-of-the-art racetracks, these
fields or currents are applied to the whole circuit. Here, we employ
micromagnetic and atomistic simulations to establish a concept for racetrack
memories free of global driving forces. Surprisingly, we realize that mixed
sequences of topologically distinct objects can be created and propagated over
far distances exclusively by local rotation of magnetization at the sample
boundaries. We reveal the dependence between the chirality of the rotation and
the direction of propagation and define the phase space where the proposed
procedure can be realized. The advantages of this approach are the exclusion of
high current and field densities as well as its compatibility with an
energy-efficient three-dimensional design.Comment: 23 pages, 7 figure