Giant Spin Transfer Torque in Atomically Thin Magnetic Bilayers

In cavity quantum electrodynamics,the multiple reflections of a photon between two mirrors defining a cavity is exploited to enhance the light-coupling of an intra-cavity atom.We show that this paradigm for enhancing the interaction of a flying particle with a localized object can be generalized to spintronics based on van der Waals 2D magnets.Upon tunneling through a magnetic bilayer,we find that the spin transfer torques per electron incidence can become orders of magnitude larger thanℏ/2,made possible by electron's multi-reflection path through the ferromagnetic monolayers as an intermediate of their angular momentum transfer.Over a broad energy range around the tunneling resonances,the damping-like spin transfer torque per electron tunneling features a universal value of(ℏ/2)tan(θ/2),depending only on the angleθbetween the magnetizations.These findings expand the scope of magnetization manipulations for high-performance and high-density storage based on van der Waals magnets.

Narrow Waveguide Based on Ferroelectric Domain Wall

Ferroelectric materials are spontaneous symmetry breaking systems that are characterized by ordered electric polarizations.Similar to its ferromagnetic counterpart,a ferroelectric domain wall can be regarded as a soft interface separating two different ferroelectric domains.Here we show that two bound state excitations of electric polarization(polar wave),or the vibration and breathing modes,can be hosted and propagate within the ferroelectric domain wall.In particular,the vibration polar wave has zero frequency gap,thus is constricted deeply inside ferroelectric domain wall,and can even propagate in the presence of local pinnings.The ferroelectric domain wall waveguide as demonstrated here offers a new paradigm in developing ferroelectric information processing units.

Enhanced Anomalous Hall Effect of Pt on an Antiferromagnetic Insulator with Fully Compensated Surface

We report a significantly enhanced anomalous Hall effect(AHE)of Pt on antiferromagnetic insulator thin film(3-unit-cell La_(0.7)Sr_(0.3)MnO_(3),abbreviated as LSMO),which is one order of magnitude larger than that of Pt on other ferromagnetic(e.g.Y_(3)Fe_(5)O_(12))and antiferromagnetic(e.g.Cr_(2)O_(3))insulator thin films.Our experiments demonstrate that the antiferromagnetic La_(0.7)Sr_(0.3)MnO_(3)with fully compensated surface suppresses the positive anomalous Hall resistivity induced by the magnetic proximity effect and facilitates the negative anomalous Hall resistivity induced by the spin Hall effect.By changing the substrate’s temperature during Pt deposition,we observed that the diffusion of Mn atoms into Pt layer can further enhance the AHE.The anomalous Hall resistivity increases with increasing temperature and persists even well above the Neel temperature(T_(N))of LSMO.The Monte Carlo simulations manifest that the unusual rise of anomalous Hall resistivity above T_(N)originates from the thermal induced magnetization in the antiferromagnetic insulator.

Inexpensive and flexible nanographene-based electrodes for ubiquitous electrocardiogram monitoring

Flexible electronics is one of the fundamental technologies for the development of electronic skin,implant wearables,or ubiquitous biosensing.In this context,graphene-derived materials have attracted great interest due to their unique properties to fulfill the demands of these applications.Here we report a simple one-step method for the fabrication of electrophysical electrodes based on the photothermal production of porous nanographene structures on the surface of flexible polyimide substrates.This approach constitutes an inexpensive alternative to the commercial medical electrodes,leading to a lower and much more stable skin–electrode contact resistance and providing comparable signal transduction.This technology has been framed inside the IoT paradigm through the development of a denoising and signal classification clustering algorithm suitable for its implementation in wearable devices.The experiments have shown promising achievements regarding noise reduction,increasing the crest factor~3.7 dB,as well as for the over 90%heart rate-monitoring accuracy.