Impact of inherent energy barrier on spin-orbit torques in magnetic-metal/semimetal heterojunctions.

Spintronic devices are based on heterojunctions of two materials with different magnetic and electronic properties. Although an energy barrier is naturally formed even at the interface of metallic heterojunctions, its impact on spin transport has been overlooked. Here, using diffusive spin Hall currents, we provide evidence that the inherent energy barrier governs the spin transport even in metallic systems. We find a sizable field-like torque, much larger than the damping-like counterpart, in Ni81Fe19/Bi0.1Sb0.9 bilayers. This is a distinct signature of barrier-mediated spin-orbit torques, which is consistent with our theory that predicts a strong modification of the spin mixing conductance induced by the energy barrier. Our results suggest that the spin mixing conductance and the corresponding spin-orbit torques are strongly altered by minimizing the work function difference in the heterostructure. These findings provide a new mechanism to control spin transport and spin torque phenomena by interfacial engineering of metallic heterostructures.

Laser CVD Growth of Uniquely <010>-oriented ß-Ga2 O3 Films on Quartz Substrate with Ultrafast Photoelectric Response.

The oriented growth of ß-Ga2 O3 films has triggered extensive interest due to the remarkable and complex anisotropy found in the ß-Ga2 O3 bulks. Remarkable properties, including stronger solar-blind ultraviolet (SBUV) absorption, better mobility, and higher thermal conductivity, are usually observed along <010> direction as compared to other low-index axes. So far, <010>-oriented ß-Ga2 O3 film growth has been hindered by the lack of suitable substrates and higher surface energy of the (010) crystal plane. Herein, the first growth of uniquely <010>-oriented ß-Ga2 O3 films on quartz substrates by laser chemical vapor deposition (LCVD) are reported. By investigating the effects of deposition temperature (Tdep ) and O2 flow rate (RO2 ) on the growth of ß-Ga2 O3 films, it is found that the formation of <010> orientation is closely related to the higher stability of oxygen close-packed planes under O-rich condition. As a result, a grain size of up to ≈2 µm and a deposition rate of up to ≈ 40 µm h-1 are obtained. Metal-semiconductor-metal (MSM) type detector based on <010>-oriented ß-Ga2 O3 film exhibits ultra-fast response speed, 1-2 orders of magnitude higher than those of most detectors based on ß-Ga2 O3 films with other orientations.

Optimizing Electromagnetic Interference Shielding of Ultrathin Nanoheterostructure Textiles through Interfacial Engineering.

Strong electromagnetic wave reflection loss concomitant with second emission pollution limits the wide applications of electromagnetic interference (EMI) shielding textiles. Decoration of textiles by using various dielectric materials has been found efficient for the development of highly efficient EMI shielding textiles, but it is still a challenge to obtain EMI shielding composites with thin thickness. A route of interfacial engineering may offer a twist to overcome these obstacles. Here, we fabricated a Ni nanoparticle/SiC nanowhisker/carbon cloth nanoheterostructure, where SiC nanowhiskers were deposited by a simple manufacturing method, namely, laser chemical vapor deposition (LCVD), directly grown on carbon cloth. Through directly constructing a Ni/SiC interface, we find that the formation of Schottky contact can influence the interfacial polarization associated with the generation of dipole electric fields, leading to an enhancement of dielectric loss. A striking feature of this interfacial engineering strategy is able to enhance the absorption of the incident electromagnetic wave while suppressing the reflection. As a result, our Ni/SiC/carbon cloth exhibits an excellent EMI shielding effectiveness of 68.6 dB with a thickness of only 0.39 mm, as well as high flexibility and long-term duration stability benefited from the outstanding mechanical properties of SiC nanowiskers, showing potential for EMI shielding applications.

Spin-orbit torque manipulated by fine-tuning of oxygen-induced orbital hybridization.

Current-induced spin-orbit torques provide an effective way to manipulate magnetization in spintronic devices, promising for fast switching applications in nonvolatile memory and logic units. Recent studies have revealed that the spin-orbit torque is strongly altered by the oxidation of heterostructures with broken inversion symmetry. Although this finding opens a new field of metal-oxide spin-orbitronics, the role of the oxidation in the spin-orbit physics is still unclear. Here, we demonstrate a marked enhancement of the spin-orbit torque induced by a fine-tuning of oxygen-induced modification of orbital hybridization. This is evidenced by a concomitant enhancement of the interface spin-orbit torque, interface spin loss, and interface perpendicular magnetic anisotropy within a narrow range of the oxidation level of metallic heterostructures. This result reveals the crucial role of the atomic-scale effects in the generation of the spin-orbit torques, opening the door to atomic-level engineering of the spin-orbit physics.

Intrinsic Spin-Orbit Torque Arising from the Berry Curvature in a Metallic-Magnet/Cu-Oxide Interface.

We report the observation of the intrinsic dampinglike spin-orbit torque (SOT) arising from the Berry curvature in metallic-magnet/CuO_{x} heterostructures. We show that a robust dampinglike SOT, an order of magnitude larger than a fieldlike SOT, is generated in the heterostructure despite the absence of the bulk spin-orbit effect in the CuO_{x} layer. Furthermore, by tuning the interfacial oxidation level, we demonstrate that the fieldlike SOT changes drastically and even switches its sign, which originates from oxygen-modulated spin-dependent disorder. These results provide important information for a fundamental understanding of the physics of the SOTs.