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Spin Hall effect, an electric generation of spin current, allows for efficient control of magnetization. Recent theory revealed that orbital Hall effect creates orbital current, which can be much larger than spin-Hall-induced spin current. However, orbital current cannot directly exert a torque on a ferromagnet, requiring a conversion process from orbital current to spin current. Here, we report two effective methods of the conversion through spin-orbit coupling engineering, which allows us to unambiguously demonstrate orbital-current-induced spin torque, or orbital Hall torque. We find that orbital Hall torque is greatly enhanced by introducing either a rare-earth ferromagnet Gd or a Pt interfacial layer with strong spin-orbit coupling in Cr/ferromagnet structures, indicating that the orbital current generated in Cr is efficiently converted into spin current in the Gd or Pt layer. Our results offer a pathway to utilize the orbital current to further enhance the magnetization switching efficiency in spin-orbit-torque-based spintronic devices. Manipulation of the magnetization is of major importance in spintronics. The authors demonstrate that an electric field triggers a transverse flow of orbital moment: the so-called orbital Hall effect. This enables the efficient magnetization control, holding the promise for fast and miniaturized memories and sensors.

Sphingosine 1-phosphate (S1P) signaling has emerged as a drug target in cerebral ischemia. Among S1P receptors, S1P 2 was recently identified to mediate ischemic brain injury. But, pathogenic mechanisms are not fully identified, particularly in view of microglial activation, a core pathogenesis in cerebral ischemia. Here, we addressed whether microglial activation is the pathogenesis of S1P 2 -mediated brain injury in mice challenged with transient middle cerebral artery occlusion (tMCAO). To suppress S1P 2 activity, its specific antagonist, JTE013 was given orally to mice immediately after reperfusion. JTE013 administration reduced the number of activated microglia and reversed their morphology from amoeboid to ramified microglia in post-ischemic brain after tMCAO challenge, along with attenuated microglial proliferation. Moreover, JTE013 administration attenuated M1 polarization in post-ischemic brain. This S1P 2 -directed M1 polarization appeared to occur in activated microglia, which was evidenced upon JTE013 exposure in vivo as suppressed M1-relevant NF-κB activation in activated microglia of post-ischemic brain. Moreover, JTE013 exposure or S1P 2 knockdown reduced expression levels of M1 markers in vitro in lipopolysaccharide-driven M1 microglia. Additionally, suppressing S1P 2 activity attenuated activation of M1-relevant ERK1/2 and JNK in post-ischemic brain or lipopolysaccharide-driven M1 microglia. Overall, our study demonstrated that S1P 2 regulated microglial activation and M1 polarization in post-ischemic brain.

Spin-orbit coupling effect in structures with broken inversion symmetry, known as the Rashba effect, facilitates spin-orbit torques (SOTs) in heavy metal/ferromagnet/oxide structures, along with the spin Hall effect. Electric-field control of the Rashba effect is established for semiconductor interfaces, but it is challenging in structures involving metals owing to the screening effect. Here, we report that the Rashba effect in Pt/Co/AlO x structures is laterally modulated by electric voltages, generating out-of-plane SOTs. This enables field-free switching of the perpendicular magnetization and electrical control of the switching polarity. Changing the gate oxide reverses the sign of out-of-plane SOT while maintaining the same sign of voltage-controlled magnetic anisotropy, which confirms the Rashba effect at the Co/oxide interface is a key ingredient of the electric-field modulation. The electrical control of SOT switching polarity in a reversible and non-volatile manner can be utilized for programmable logic operations in spintronic logic-in-memory devices. A major challenge for spin based electronics is the electrical control of magnetization. Here, Kang et al demonstrate how electric field control of the Rashba effect in a Pt/Co/AlOx can enable control of the spin-orbit torque and allow for field free switching of the magnetization.

Spin Hall nano-oscillators (SHNOs) exploiting current-driven magnetization auto-oscillation have recently received much attention because of their potential for neuromorphic computing. Widespread applications of neuromorphic devices with SHNOs require an energy-efficient method of tuning oscillation frequency over broad ranges and storing trained frequencies in SHNOs without the need for additional memory circuitry. While the voltage-driven frequency tuning of SHNOs has been demonstrated, it was volatile and limited to megahertz ranges. Here, we show that the frequency of SHNOs is controlled up to 2.1 GHz by an electric field of 1.25 MV/cm. The large frequency tuning is attributed to the voltage-controlled magnetic anisotropy (VCMA) in a perpendicularly magnetized Ta/Pt/[Co/Ni] n /Co/AlO x structure. Moreover, the non-volatile VCMA effect enables cumulative control of the frequency using repetitive voltage pulses which mimic the potentiation and depression functions of biological synapses. Our results suggest that the voltage-driven frequency tuning of SHNOs facilitates the development of energy-efficient neuromorphic devices. Spin-hall nano-oscillators are a variation on spin-torque nano-oscillators, where the spin-Hall effect is used to drive oscillations, however past examples have had limited frequency tunability. Here, Choi et al demonstrate spin-hall oscillators with wide voltage controlled frequency tunability.

Interconversion between charge and spin through spin-orbit coupling lies at the heart of condensed-matter physics. In normal metal/ferromagnet bilayers, a concerted action of the interconversions, the spin Hall effect and its inverse effect of normal metals, results in spin Hall magnetoresistance, whose sign is always positive regardless of the sign of spin Hall conductivity of normal metals. Here we report that the spin Hall magnetoresistance of Ta/NiFe bilayers is negative, necessitating an additional interconversion process. Our theory shows that the interconversion owing to interfacial spin-orbit coupling at normal metal/ferromagnet interfaces can give rise to negative spin Hall magnetoresistance. Given that recent studies found the conversion from charge currents to spin currents at normal metal/ferromagnet interfaces, our work provides a missing proof of its reciprocal spin-current-to-charge-current conversion at same interface. Our result suggests that interfacial spin-orbit coupling effect can dominate over bulk effects, thereby demanding interface engineering for advanced spintronics devices. In normal metal/ferromagnet bilayers, the spin Hall magnetoresistance originating from the spin Hall effect of normal metal possesses positive sign regardless of the sign of spin Hall conductivity of normal metal. Here, the authors report negative spin Hall magnetoresistance of Ta/NiFe bilayers due to interfacial spin orbit coupling at interfaces.

Photoluminescence (PL), a photo-excited spontaneous emission process, provides a wealth of optical and electronic properties of materials, which enable microscopic and spectroscopic imaging, biomedical sensing and diagnosis, and a range of photonic device applications. However, conventional far-field PL measurements have limitations in sensitivity and spatial resolution, especially to investigate single nano-materials or nano-scale dimension of them. In contrast, tip-enhanced photoluminescence (TEPL) nano-spectroscopy provides an extremely high sensitivity with <10 nm spatial resolution, which allows the desired nano-scale characterizations. With outstanding and unique optical properties, low-dimensional quantum materials have recently attracted much attention, and TEPL characterizations, i. e., probing and imaging, and even control at the nano-scale, have been extensively studied. In this review, we discuss the fundamental working mechanism of PL enhancement by plasmonic tip, and then highlight recent advances in TEPL studies for low-dimensional quantum materials. Finally, we discuss several remaining challenges of TEPL nano-spectroscopy and nano-imaging, such as implementation in non-ambient media and in situ environments, limitations in sample structure, and control of near-field polarization, with perspectives of the approach and its applications.

Frailty is a common geriatric syndrome characterized by increased risk of disability, hospitalization, and mortality. Hypertension (HTN) is one of the most common chronic medical conditions in the elderly. However, there have been few studies regarding the association between frailty and HTN prevalence, treatment, and control rates. We analyzed data of 4,352 older adults (age ≥ 65 years) from the fifth Korea National Health and Nutrition Examination Survey. We constructed a frailty index based on 42 items and classified participants as robust, pre-frail, or frail. Of the subjects, 2,697 (62.0%) had HTN and 926 (21.3%) had pre-HTN. Regarding frailty status, 721 (16.6%), 1,707 (39.2%), and 1,924 (44.2%) individuals were classified as robust, pre-frail and frail, respectively. HTN prevalence was higher in frail elderly (67.8%) than pre-frail (60.8%) or robust elderly (49.2%) ( P  < 0.001). Among hypertensive patients, frail elderly were more likely to be treated than pre-frail or robust elderly ( P  < 0.001), but the proportion of patients whose blood pressure was under control ( < 150/90 mmHg) was lower in frail elderly ( P  = 0.005). Considering the adverse cardiovascular outcomes associated with frailty, more attention should be paid to the blood pressure control of the frail elderly.

The formation of hydrogen blisters in the fabrication of tunnelling oxide passivating contact (TOPCon) solar cells critically degrades passivation. In this study, we investigated the formation mechanism of blisters during the fabrication of TOPCons for crystalline silicon solar cells and the suppression of such blisters. We tested the effects of annealing temperature and duration, surface roughness, and deposition temperature on the blister formation, which was suppressed in two ways. First, TOPCon fabrication on a rough surface enhanced adhesion force, resulting in reduced blister formation after thermal annealing. Second, deposition or annealing at higher temperatures resulted in the reduction of hydrogen in the film. A sample fabricated through low-pressure chemical vapor deposition at 580 °C was free from silicon–hydrogen bonds and blisters after the TOPCon structure was annealed. Remarkably, samples after plasma-enhanced chemical vapor deposition at 300, 370, and 450 °C were already blistered in the as-deposited state, despite low hydrogen contents. Analysis of the hydrogen incorporation, microstructure, and deposition mechanism indicate that in plasma-enhanced chemical vapor deposition (PECVD) deposition, although the increase of substrate temperature reduces the hydrogen content, it risks the increase of porosity and molecular-hydrogen trapping, resulting in even more severe blistering.

Background Oxidative stress is a key driver of accelerated ageing, and gamma‐glutamyl transferase (GGT), an essential enzyme involved in the metabolism of glutathione, a major antioxidant, plays a pivotal role in the generation of free radical species. This study aimed to explore the potential utility of circulating GGT as a biomarker of frailty, which reflects biological ageing and overall health status. Methods This cross‐sectional, population‐based study included 2526 community‐dwelling adults aged 65 years and older, using data from the Korea National Health and Nutrition Examination Survey. Frailty was assessed using a deficit accumulation frailty index (FI) derived from 36 items encompassing physical, cognitive, psychological, and social domains. Participants were categorised as nonfrail (FI ≤ 0.15), prefrail (0.15 < FI ≤ 0.25), or frail (FI > 0.25). Serum GGT levels were determined using an enzymatic activity assay. Results After adjusting for potential confounders including age, body mass index, socioeconomic status, lifestyle factors, and medical history, serum GGT levels were 26.0% higher in frail men than in nonfrail men (p = 0.010). Amongst men, serum GGT concentrations were positively correlated with the FI (p = 0.001), and each standard deviation increase in serum GGT was associated with a 1.36‐fold higher odds of frailty (p = 0.001). Additionally, older men in the highest GGT quartile exhibited a significantly higher FI and a 2.08‐fold increased odds of frailty compared to those in the lowest quartile (p = 0.010 and p = 0.019, respectively). In women, however, no significant association was observed between serum GGT levels and frailty. Conclusion Elevated serum GGT levels were significantly associated with frailty in older men, suggesting their potential as a biomarker of biological ageing. Nonetheless, the cross‐sectional design precludes causal inference, and longitudinal studies are warranted to explore whether elevated GGT contributes to the onset or progression of frailty over time.

Motor imagery (MI) for target-oriented movements, which is a basis for functional activities of daily living, can be more appropriate than non-target-oriented MI as tasks to promote motor recovery or brain-computer interface (BCI) applications. This study aimed to explore different characteristics of brain activation among target-oriented kinesthetic imagery (KI) and visual imagery (VI) in the first-person (VI-1) and third-person (VI-3) perspectives. Eighteen healthy volunteers were evaluated for MI ability, trained for the three types of target-oriented MIs, and scanned using 3 T functional magnetic resonance imaging (fMRI) under MI and perceptual control conditions, presented in a block design. Post-experimental questionnaires were administered after fMRI. Common brain regions activated during the three types of MI were the left premotor area and inferior parietal lobule, irrespective of the MI modalities or perspectives. Contrast analyses showed significantly increased brain activation only in the contrast of KI versus VI-1 and KI versus VI-3 for considerably extensive brain regions, including the supplementary motor area and insula. Neural activity in the orbitofrontal cortex and cerebellum during VI-1 and KI was significantly correlated with MI ability measured by mental chronometry and a self-reported questionnaire, respectively. These results can provide a basis in developing MI-based protocols for neurorehabilitation to improve motor recovery and BCI training in severely paralyzed individuals.