13 research outputs found
Magneto-Optical Imaging of Magnetic-Domain Pinning Induced by Chiral Molecules
Chiral molecules have the potential for creating new magnetic devices by
locally manipulating the magnetic properties of metallic surfaces. When chiral
polypeptides chemisorb onto ferromagnets they can induce magnetization locally
by spin exchange interactions. However, direct imaging of surface magnetization
changes induced by chiral molecules was not previously realized. Here, we use
Magneto-optical Kerr microscopy to image domains in thin films and show that
chiral polypeptides strongly pin domains, increasing the coercive field
locally. In our study, we also observe a rotation of the easy magnetic axis
towards the out-of-plane, depending on the sample's domain size and the
adsorption area. These findings show the potential of chiral molecules to
control and manipulate magnetization and open new avenues for future research
on the relationship between chirality and magnetization.Comment: 11 pages, 4 figure
Detection of long-range orbital-Hall torques
We report and quantify a large orbital-Hall torque generated by Nb and Ru,
which we identify from a strong dependence of torques on the ferromagnets. This
is manifested as a sign reversal and strong enhancement in the damping-like
torques measured in Nb (or Ru)/Ni bilayers as compared to Nb (or Ru)/FeCoB
bilayers. The long-range nature of orbital transport in the ferromagnet is
revealed by the thickness dependences of Ni in Nb (or Ru)/Ni bilayers which are
markedly different from the regular spin absorption in the ferromagnet that
takes place within a few angstroms and thus it uniquely distinguishes the
orbital Hall torque from the spin Hall torque
Fiber-tip spintronic terahertz emitters
Spintronic terahertz emitters promise terahertz sources with an unmatched
broad frequency bandwidth that are easy to fabricate and operate, and therefore
easy to scale at low cost. However, current experiments and proofs of concept
rely on free-space ultrafast pump lasers and rather complex benchtop setups.
This contrasts with the requirements of widespread industrial applications,
where robust, compact, and safe designs are needed. To meet these requirements,
we present a novel fiber-tip spintronic terahertz emitter solution that allows
spintronic terahertz systems to be fully fiber-coupled. Using single-mode fiber
waveguiding, the newly developed solution naturally leads to a simple and
straightforward terahertz near-field imaging system with a 90%-10%
knife-edge-response spatial resolution of 30
Poor Doors in Erlangen: Environment-related microsegregation under conditions of reurbanisation
In der sich im Zuge der Reurbanisierung verschĂ€rfenden Konkurrenz um stĂ€dtische Ressourcen gestalten sich Prozesse der Segregation zunehmend kleinrĂ€umiger. Eine Fallstudie in Erlangen zeigt, wie bei den Planungen eines Quartiers im Röthelheimpark und der Rathenausiedlung bevorzugte Wohnlagen geschaffen werden, nicht zuletzt durch die Einrichtung benachteiligter Wohnlagen. Es entstehen PhĂ€nomene einer Mikrosegregation auf Quartiersebene, die ĂŒber die gĂ€ngigen Methoden statistischer Messung kaum noch empirisch zu erfassen sind. Die besondere Brisanz erhĂ€lt das Thema durch die Tatsache, dass hierbei gesundheitliche Risiken ungleich verteilt werden, denn Umweltbelastungen werden gezielt den Ă€rmeren Bewohner_innengruppen zugemutet, wĂ€hrend Umweltressourcen den Wohlhabenden zugutekommen.As competition for urban resources intensifies as a result of reurbanisation, segregation processes are becoming increasingly small-scale. A case study in Erlangen shows how planning in the district of Röthelheimpark and Rathenausiedlung creates preferred residential locations, not least due to the establishment of disadvantaged sites. There are phenomena of micro segregation at neighbourhood level which can hardly be empirically recorded using conventional methods of statistical measurement. The topic is particularly explosive due to the fact that health risks are unequally distributed, because environmental pollution is specifically imposed on poorer groups of residents, while environmental resources benefit the wealthy
Harnessing Orbital-to-Spin Conversion of Interfacial Orbital Currents for Efficient Spin-Orbit Torques
Current-induced spin-orbit torques (SOTs) allow for the efficient electrical manipulation of magnetism in spintronic devices. Engineering the SOT efficiency is a key goal that is pursued by maximizing the active interfacial spin accumulation or modulating the nonequilibrium spin density that builds up through the spin Hall and inverse spin galvanic effects. Regardless of the origin, the fundamental requirement for the generation of the current-induced torques is a net spin accumulation. We report on the large enhancement of the SOT efficiency in thulium iron garnet (TmIG)/Pt by capping with a CuOx layer. Considering the weak spin-orbit coupling (SOC) of CuOx, these surprising findings likely result from an orbital current generated at the interface between CuOx and Pt, which is injected into the Pt layer and converted into a spin current by strong SOC. The converted spin current decays across the Pt layer and exerts a ânonlocalâ torque on TmIG. This additional torque leads to a maximum colossal enhancement of the SOT efficiency of a factor 16 for 1.5 nm of Pt at room temperature, thus opening a path to increase torques while at the same time offering insights into the underlying physics of orbital transport, which has so far been elusive
Tailoring Magnetic Properties and Suppressing Anisotropy in Permalloy Films by Deposition in a Rotating Magnetic Field
<p>We investigate the optimal deposition conditions for permalloy (Ni81Fe19) thin films fabricated via magnetron sputtering to achieve soft magnetic films for magnetoresistive sensing applications. The films are grown with different deposition techniques such as sputtering and molecular-beam epitaxy and parameters, including varying inert gas pressure and deposition power, and with different magnetic fields applied during the growth. Our approach enables sputtering of permalloy films with low coercivity while keeping high anisotropic magnetoresistance values. We develop a robust method to characterize the intrinsic magnetic anisotropy of the films that is not dominated by local defects and we demonstrate the possibility of magnetic anisotropy suppression via implementing a rotating magnetic field during sputtering.</p>
Enhanced thermally-activated skyrmion diffusion with tunable effective gyrotropic force
Abstract Magnetic skyrmions, topologically-stabilized spin textures that emerge in magnetic systems, have garnered considerable interest due to a variety of electromagnetic responses that are governed by the topology. The topology that creates a microscopic gyrotropic force also causes detrimental effects, such as the skyrmion Hall effect, which is a well-studied phenomenon highlighting the influence of topology on the deterministic dynamics and drift motion. Furthermore, the gyrotropic force is anticipated to have a substantial impact on stochastic diffusive motion; however, the predicted repercussions have yet to be demonstrated, even qualitatively. Here we demonstrate enhanced thermally-activated diffusive motion of skyrmions in a specifically designed synthetic antiferromagnet. Suppressing the effective gyrotropic force by tuning the angular momentum compensation leads to a more than 10 times enhanced diffusion coefficient compared to that of ferromagnetic skyrmions. Consequently, our findings not only demonstrate the gyro-force dependence of the diffusion coefficient but also enable ultimately energy-efficient unconventional stochastic computing
Fiber-tip spintronic terahertz emitters
<p>Spintronic terahertz emitters promise terahertz sources with an unmatched broad frequency bandwidth that are easy to fabricate and operate, and therefore easy to scale at low cost. However, current experiments and proofs of concept rely on free-space ultrafast pump lasers and rather complex benchtop setups. This contrasts with the requirements of widespread industrial applications, where robust, compact, and safe designs are needed. To meet these requirements, we present a novel fiber-tip spintronic terahertz emitter solution that allows spintronic terahertz systems to be fully fiber-coupled. Using single-mode fiber waveguiding, the newly developed solution naturally leads to a simple and straightforward terahertz near-field imaging system with a 90%-10% knife-edge-response spatial resolution of 30 ÎŒm.</p>
Controlling the Interlayer DzyaloshinskiiâMoriya Interaction by Electrical Currents
The recently discovered interlayer DzyaloshinskiiâMoriya
interaction (IL-DMI) in multilayers with perpendicular magnetic anisotropy
favors canting of spins in the in-plane direction. It could thus stabilize
intriguing spin textures such as Hopfions. A key requirement for nucleation
is to control the IL-DMI. Therefore, we investigate the influence
of an electric current on a synthetic antiferromagnet with growth-induced
IL-DMI. The IL-DMI is quantified by using out-of-plane hysteresis
loops of the anomalous Hall effect while applying a static in-plane
magnetic field at varied azimuthal angles. We observe a shift in the
azimuthal dependence with an increasing current, which we conclude
to originate from the additional in-plane symmetry breaking introduced
by the current flow. Fitting the angular dependence, we demonstrate
the presence of an additive current-induced term that linearly increases
the IL-DMI in the direction of current flow. This opens the possibility
of easily manipulating 3D spin textures by currents