Persistent ferromagnetic ground state in pristine and Ni-doped FeGaTe flakes.

Room-temperature magnetism and its stability upon miniaturization are essential characteristics required for materials for spintronic devices and information storage. Among various candidates, FeGaTe stands out due to its high Curie temperature and strong perpendicular magnetic anisotropy (PMA), recently gaining large attention as one of the promising candidate materials for spintronics applications. In this study, we measured the thickness-dependent ferromagnetic properties of FeGaTe and (FeNi)GaTe (with x = 0.

Spin-orbit-splitting-driven nonlinear Hall effect in NbIrTe.

The Berry curvature dipole (BCD) serves as a one of the fundamental contributors to emergence of the nonlinear Hall effect (NLHE). Despite intense interest due to its potential for new technologies reaching beyond the quantum efficiency limit, the interplay between BCD and NLHE has been barely understood yet in the absence of a systematic study on the electronic band structure. Here, we report NLHE realized in NbIrTe that persists above room temperature coupled with a sign change in the Hall conductivity at 150 K.

Voltage control of magnetism in FeGeTe/InSe van der Waals ferromagnetic/ferroelectric heterostructures.

We investigate the voltage control of magnetism in a van der Waals (vdW) heterostructure device consisting of two distinct vdW materials, the ferromagnetic FeGeTe and the ferroelectric InSe. It is observed that gate voltages applied to the FeGeTe/InSe heterostructure device modulate the magnetic properties of FeGeTe with significant decrease in coercive field for both positive and negative voltages. Raman spectroscopy on the heterostructure device shows voltage-dependent increase in the in-plane InSe and FeGeTe lattice constants for both voltage polarities.

Exchange Bias in Weakly Interlayer-Coupled van der Waals Magnet FeGeTe.

van der Waals (vdW) magnetic materials provide an ideal platform to study low-dimensional magnetism. However, observations of magnetic characteristics of these layered materials truly distinguishing them from conventional magnetic thin film systems have been mostly lacking. In an effort to investigate magnetic properties unique to vdW magnetic materials, we examine the exchange bias effect, a magnetic phenomenon emerging at the ferromagnetic-antiferromagnetic interface.

Controlling the Magnetic Anisotropy of the van der Waals Ferromagnet FeGeTe through Hole Doping.

Identifying material parameters affecting properties of ferromagnets is key to optimized materials that are better suited for spintronics. Magnetic anisotropy is of particular importance in van der Waals magnets, since it not only influences magnetic and spin transport properties, but also is essential to stabilizing magnetic order in the two-dimensional limit. Here, we report that hole doping effectively modulates the magnetic anisotropy of a van der Waals ferromagnet and explore the physical origin of this effect.

Optical control of the layer degree of freedom through Wannier-Stark states in polar 3R MoS.

Electrons in two-dimensional layered crystals gain a discrete positional degree of freedom over layers. We propose the two-dimensional transition metal dichalcogenide homostructure with polar symmetry as a prototypical platform where the degrees of freedom for the layers and valleys can be independently controlled through an optical method. In 3R MoS, a model system, the presence of the spontaneous polarization and built-in electric field along the stacking axis is theoretically proven by the density functional theory.

All-Electrical Measurement of Interfacial Dzyaloshinskii-Moriya Interaction Using Collective Spin-Wave Dynamics.

Dzyaloshinskii-Moriya interaction (DMI), which arises from the broken inversion symmetry and spin-orbit coupling, is of prime interest as it leads to a stabilization of chiral magnetic order and provides an efficient manipulation of magnetic nanostructures. Here, we report all-electrical measurement of DMI using propagating spin wave spectroscopy based on the collective spin wave with a well-defined wave vector. We observe a substantial frequency shift of spin waves depending on the spin chirality in Pt/Co/MgO structures.

Hydrodynamic assembly of conductive nanomesh of single-walled carbon nanotubes using biological glue.

A hydrodynamic phenomenon is used to assemble a large-scale conductive nanomesh of single-walled carbon nanotubes (SWNTs) with exceptional control of the nanostructure. This is accomplished by a biological material with nanoscale features and a strong binding affinity toward SWNTs. The biological material also presents a unique glue effect for the assembly.

Doping against the native propensity of MoS2: degenerate hole doping by cation substitution.

Layered transition metal dichalcogenides (TMDs) draw much attention as the key semiconducting material for two-dimensional electrical, optoelectronic, and spintronic devices. For most of these applications, both n- and p-type materials are needed to form junctions and support bipolar carrier conduction. However, typically only one type of doping is stable for a particular TMD.

Spin nano-oscillator-based wireless communication.

Spin-torque nano-oscillators (STNOs) have outstanding advantages of a high degree of compactness, high-frequency tunability, and good compatibility with the standard complementary metal-oxide-semiconductor process, which offer prospects for future wireless communication. There have as yet been no reports on wireless communication using STNOs, since the STNOs also have notable disadvantages such as lower output power and poorer spectral purity in comparison with those of LC voltage-controlled oscillators. Here we show that wireless communication is achieved by a proper choice of modulation scheme despite these drawbacks of STNOs.

Intrinsic and extrinsic performance limits of graphene devices on SiO2.

The linear dispersion relation in graphene gives rise to a surprising prediction: the resistivity due to isotropic scatterers, such as white-noise disorder or phonons, is independent of carrier density, n. Here we show that electron-acoustic phonon scattering is indeed independent of n, and contributes only 30 Omega to graphene's room-temperature resistivity. At a technologically relevant carrier density of 1 x1012 cm-2, we infer a mean free path for electron-acoustic phonon scattering of >2 microm and an intrinsic mobility limit of 2 x 105 cm2 V-1 s-1.