We report a novel microwave plasma enhanced chemical vapor deposition strategy for the efficient synthesis of multilayer graphene nanoflake films (MGNFs) on Si substrates. The constituent graphene nanoflakes have a highly graphitized knife‐edge structure with a 2–3 nm thick sharp edge and show a preferred vertical orientation with respect to the Si substrate as established by near‐edge X‐ray absorption fine structure spectroscopy. The growth rate is approximately 1.6 µm min−1, which is 10 times faster than the previously reported best value. The MGNFs are shown to demonstrate fast electron‐transfer (ET) kinetics for the Fe(CN)63−/4− redox system and excellent electrocatalytic activity for simultaneously determining dopamine (DA), ascorbic acid (AA) and uric acid (UA). Their biosensing DA performance in the presence of common interfering agents AA and UA is superior to other bare solid‐state electrodes and is comparable only to that of edge plane pyrolytic graphite. Our work here, establishes that the abundance of graphitic edge planes/defects are essentially responsible for the fast ET kinetics, active electrocatalytic and biosensing properties. This novel edge‐plane‐based electrochemical platform with the high surface area and electrocatalytic activity offers great promise for creating a revolutionary new class of nanostructured electrodes for biosensing, biofuel cells and energy‐conversion applications.

DAWN is a generic data analysis software platform that has been developed for use at synchrotron beamlines for data visualization and analysis. Its generic design makes it suitable for use in a range of scientific and engineering applications.

Magnetic skyrmions are chiral spin textures that hold great promise as nanoscale information carriers. Since their first observation at room temperature, progress has been made in their currentinduced manipulation, with fast motion reported in stray-field-coupled multilayers. However, the complex spin textures with hybrid chiralities and large power dissipation in these multilayers limit their practical implementation and the fundamental understanding of their dynamics. Here, we report on the current-driven motion of Néel skyrmions with diameters in the 100-nm range in an ultrathin Pt/Co/MgO trilayer. We find that these skyrmions can be driven at a speed of 100 m s −1 and exhibit a drive-dependent skyrmion Hall effect, which is accounted for by the effect of pinning. Our experiments are well substantiated by an analytical model of the skyrmion dynamics as well as by micromagnetic simulations including material inhomogeneities. This good agreement is enabled by the simple skyrmion spin structure in our system and a thorough characterization of its static and dynamical properties.

We use time- and angle-resolved photoemission spectroscopy with sub-30-fs extreme-ultraviolet pulses to map the time- and momentum-dependent electronic structure of photoexcited 1T-TaS(2). This compound is a two-dimensional Mott insulator with charge-density wave ordering. Charge order, evidenced by splitting between occupied subbands at the Brillouin zone boundary, melts well before the lattice responds. This challenges the view of a charge-density wave caused by electron-phonon coupling and Fermi-surface nesting alone, and suggests that electronic correlations play a key role in driving charge order.

We show that superconducting interlayer coupling, which coexists with and is depressed by stripe order in La1.885Ba0.115CuO4, can be enhanced by excitation with near-infrared laser pulses. For temperatures lower than Tc = 13 K, we observe a blue-shift of the equilibrium Josephson plasma resonance, detected by terahertzfrequency reflectivity measurements. Key to this measurement is the ability to probe the optical properties at frequencies as low as 150 GHz, detecting the weak interlayer coupling strengths. For T > Tc a similar plasma resonance, absent at equilibrium, is induced up to the spin-ordering temperature TSO ≃ 40 K. These effects are reminiscent but qualitatively different from the light-induced superconductivity observed by resonant phonon excitation in La1.675Eu0.2Sr0.125CuO6.5. Importantly, enhancement of the below-Tc interlayer coupling and its appearance above Tc are preferentially achieved when the nearinfrared pump light is polarized perpendicular to the superconducting planes, likely due to more effective melting of stripe order and the less effective excitation of quasiparticles from the Cooper pair condensate when compared to in-plane excitation.

At low-temperatures (T < T N =110 K < T CO/OO =220 K), single-layer La 0.5 Sr 1.5 MnO 4 exhibits CE-type charge, spin and orbital order, characterized by in-plane "zig-zag" ferromagnetic chains. These chains are antiferromagnetically coupled with one another, in and out of plane [11,12,13]. Resonant soft Xray diffraction is directly sensitive to this spin and orbital order, when the incident photon energy is tuned to the 2p→3d transitions (Mn L 2,3 edges), and provides both momentum-dependent and spectroscopic information [14,15]. Figure 1 The temporal evolution of the integrated diffraction spot intensity at the magnetic (¼ ¼ ½) wave vector, obtained from the fits as described above, is reported in Figure 2(a). Diffraction was reduced by 8%, with a single time constant of 12.2 ps. For comparison, we display the significantly faster response response measured after excitation with 5-mJ/cm 2 pulses at 800-nm wavelength [23,24,25], which reveals a prompt collapse of magnetic order on the 250 fs time resolution of the experiment.This observation of different timescales is evidence that lattice driven magnetic disordering must follow a different physical path than for electronic excitation in the near infrared.In Figure 2 timescale and amplitude, with the orbital order only reduced by only 3% with a single-exponential decay time of 6.3 ps. We note that this lattice-driven orbital disordering is slower than was observed previously by time-dependent optical birefringence [19]. However, time dependent optical birefringence, proportional to the orbital order parameter squared in equilibrium [18], is a less direct method than the resonant x-ray diffraction used here.Throughout these dynamics, we see no transient change in the position and width of the scattered diffraction spots for either order and conclude that the correlation lengths are not perturbed. This is shown in Figure 2(c) where we exemplarily plot the transient width of the magnetic diffraction spot together with its peak position. The latter is constant within < 1×10 -5 (calculated standard deviation). , among which we find the Raman-active Jahn-Teller mode depicted in Fig. 3(c). Thus, according to the IRS model, rectification of the mid-infrared mode is able to relax the cooperative Jahn-Teller distortion, which has no infrared activity and thus cannot be driven directly by mid-infrared excitation. Importantly, the Jahn-Teller mode shown in Fig. 3(c) relaxes the splitting between crystal field levels and reduces the ordering of the orbitals. In turn, this weakens the exchange interaction that stabilizes the CE-type order and would thus lead to a smaller equilibrium magnetization, or to a lower equivalent Neel temperature.We stress that in contrast to the case of La 0.7 Sr 0.3 MnO 3 [27], in which the envelope of the infraredactive E u mode drives a low-frequency 1.2-THz rotational (E g ) mode impulsively, the Jahn-Teller A g mode has a higher frequency (15 THz) than the inverse 130-fs envelope of the infrared-active mode.Thus, in La 0.5 Sr 1.5 MnO 4 , the A...

Antiferromagnets have several favourable properties as active elements in spintronic devices, including ultra-fast dynamics, zero stray fields and insensitivity to external magnetic fields . Tetragonal CuMnAs is a testbed system in which the antiferromagnetic order parameter can be switched reversibly at ambient conditions using electrical currents . In previous experiments, orthogonal in-plane current pulses were used to induce 90° rotations of antiferromagnetic domains and demonstrate the operation of all-electrical memory bits in a multi-terminal geometry . Here, we demonstrate that antiferromagnetic domain walls can be manipulated to realize stable and reproducible domain changes using only two electrical contacts. This is achieved by using the polarity of the current to switch the sign of the current-induced effective field acting on the antiferromagnetic sublattices. The resulting reversible domain and domain wall reconfigurations are imaged using X-ray magnetic linear dichroism microscopy, and can also be detected electrically. Switching by domain-wall motion can occur at much lower current densities than those needed for coherent domain switching.

Diffraction is used to determine the spatial and temporal evolution of the magnetic disordering. We observe a magnetic melt front that grows from the substrate interface into the film, at a speed that suggests electronically driven propagation.Light control and ultrafast phase front propagation at hetero-interfaces may lead to new opportunities in optomagnetism, for example by driving domain wall motion to transport information across suitably designed devices. 3/25! ! !In transition metal oxides, rearrangements in electronic and magnetic properties can be triggered by the application of magnetic [5] and electric fields [6], or pressure [7,8].Switching has also been demonstrated in these materials using femtosecond optical excitation, at near-visible [9,10,11,12,13,14,15], mid-infrared [16,17,18,19,20] edge. The bandwidth of the X-ray pulses was reduced to below 1 eV by a grating monochromator. Diffracted X-rays were detected as function of the time delay relative to the mid-infrared excitation pulses. An avalanche photodiode enabled pulse-to-pulse normalization of the diffracted to the incident light intensity. where the latter is limited by the jitter between the FEL and the optical laser. We compare these dynamics to the time needed for the film to become metallic, as measured by the transient reflectivity in the 1−5 THz range induced by the same mid-infrared excitation (green dots in Fig. 1(d)). These two similar timescales, which reflect only average changes over the whole film, suggest an intimate connection between the insulator-to-metal transition and the melting of magnetic order.In Figure 2, we plot the transient θ-2θ scans for the (1/4 1/4 1/4) diffraction peak, sensitive to the out-of-plane antiferromagnetic ordering. In equilibrium, i.e. at negative time delay, a narrow diffraction peak and Laue oscillations are observed, attesting to the presence of magnetic order across the entire 30-nm film height, with sharp magnetic boundaries.Figure 2 further shows that a significant peak broadening and a suppression of the Laue oscillations accompany the strong photo-induced reduction in peak intensity. The broadening of the diffraction peak implies that the excitation melts the magnetic order only over a fraction of the film along the sample growth direction. Secondly, the suppression of the Laue oscillations indicates that the boundary between the ordered and disordered regions of the film is not sharp.We also find that throughout these dynamics the in-plane correlation length, as measured by transverse rocking curves (θ scans), remains unchanged (see Supplementary 6/25! ! ! Information). Hence, the dynamics discussed here are one dimensional, evolving along the sample growth direction.!The spatial distribution of the magnetic order at a time delay τ was analyzed quantitatively with the following expression for kinematic diffractionHere, the magnetic profile is represented by the space-and time-dependent structure factor F(z,τ), where ! = 4! sin ! ! is the magnitude of the scattering wave vector (with θ th...