Widespread applications of magnetic devices require an efficient means to manipulate the local magnetization. One mechanism is the electrical spin-transfer torque associated with electron-mediated ...spin currents; however, this suffers from substantial energy dissipation caused by Joule heating. We experimentally demonstrated an alternative approach based on magnon currents and achieved magnon-torque-induced magnetization switching in Bi
Se
/antiferromagnetic insulator NiO/ferromagnet devices at room temperature. The magnon currents carry spin angular momentum efficiently without involving moving electrons through a 25-nanometer-thick NiO layer. The magnon torque is sufficient to control the magnetization, which is comparable with previously observed electrical spin torque ratios. This research, which is relevant to the energy-efficient control of spintronic devices, will invigorate magnon-based memory and logic devices.
Terahertz emission spectroscopy (TES) has recently played an important role in unveiling the spin dynamics at a terahertz (THz) frequency range. So far, ferromagnetic/nonmagnetic heterostructures ...have been intensively studied as THz sources. Compensated magnets such as a ferrimagnet (FIM) and antiferromagnet (AFM) are other types of magnetic materials with interesting spin dynamics. In this work, TES from compensated magnetic heterostructures including CoGd FIM alloy or IrMn AFM layers is studied. Systematic measurements on composition and temperature dependences of THz emission from CoGd/Pt bilayer structures are conducted. It is found that the emitted THz field is determined by the net spin polarization of the laser‐induced spin current rather than the net magnetization. The temperature robustness of the FIM‐based THz emitter is also demonstrated. On the other hand, an AFM plays a different role in THz emission. The IrMn/Pt bilayer shows negligible THz signals, whereas Co/IrMn induces sizable THz outputs, indicating that IrMn is not a good spin current generator, but a good detector. These results not only suggest that a compensated magnet can be utilized for robust THz emission, but also provide a new approach to study the magnetization dynamics especially near the magnetization compensation point.
An efficient terahertz (THz) emission from compensated ferrimagnet/nonmagnetic metallic heterostructures is demonstrated. The THz emission is determined by the net spin polarization rather than the net magnetization. Antiferromagnet plays a role as an effective spin sink in THz emission. Ferrimagnet‐based THz emitters are promising not only for THz applications, but also offering an opportunity to study the magnetization dynamics.
Abstract The ability to electrically manipulate antiferromagnetic magnons, essential for extending the operating speed of spintronic devices into the terahertz regime, remains a major challenge. This ...is because antiferromagnetic magnetism is challenging to perturb using traditional methods such as magnetic fields. Recent developments in spin-orbit torques have opened a possibility of accessing antiferromagnetic magnetic order parameters and controlling terahertz magnons, which has not been experimentally realised yet. Here, we demonstrate the electrical manipulation of sub-terahertz magnons in the α -Fe 2 O 3 /Pt antiferromagnetic heterostructure. By applying the spin-orbit torques in the heterostructure, we can modify the magnon dispersion and decrease the magnon frequency in α -Fe 2 O 3 , as detected by time-resolved magneto-optical techniques. We have found that optimal tuning occurs when the Néel vector is perpendicular to the injected spin polarisation. Our results represent a significant step towards the development of electrically tunable terahertz spintronic devices.
An ultra‐broadband terahertz (THz) emitter covering a wide range of frequencies from 0.1 to 10 THz is highly desired for spectroscopy applications. So far, spintronic THz emitters have been proven as ...one class of efficient THz sources with a broadband spectrum while the performance in the lower THz frequency range (0.1–0.5 THz) limits its applications. In this work, a novel concept of a current‐enhanced broad spectrum from spintronic THz emitters combined with semiconductor materials is demonstrated. A 2–3 order enhancement of the THz signals in a lower THz frequency range (0.1–0.5 THz) is observed, in addition to a comparable performance at higher frequencies from this hybrid emitter. With a bias current, there is a photoconduction contribution from semiconductor materials, which can be constructively interfered with the THz signals generated from the magnetic heterostructures driven by the inverse spin Hall effect (ISHE). These findings push forward the utilization of metallic heterostructure‐based THz emitters on the ultra‐broadband THz emission spectroscopy.
A novel ultra‐broadband spintronic terahertz (THz) emitter enhanced by a current modulation through the semiconductor channel is demonstrated for the first time. A significant enhancement of the THz signal (up to 2–3 orders) in the frequency range from 0.1 to 0.5 THz without compromising the performance at higher frequencies is achieved, as compared with the typical spin‐based emitters.
Although statins are an effective strategy for the secondary prevention of atherosclerotic cardiovascular disease (ASCVD) in the general population, the benefits for dialysis patients are ...controversial. We sought to assess trends of statin use and evaluate outcomes of statin therapy in dialysis patients with different types of ASCVD.
This nationwide retrospective population-based cohort study using data from the Korean National Health Insurance Service included adult patients (aged ≥ 18 years) undergoing chronic dialysis who had an initial ASCVD event in the time period of 2013 to 2018. Annual trends of statin use according to age, sex, and ASCVD types were analyzed. The association between 1-year mortality and statin use was examined using multivariable Cox proportional hazards regression analyses.
Among 17,242 subjects, 9,611(55.7%) patients were statin users. The overall prevalence of statin use increased from 52.9% in 2013 to 57.7% in 2018; the majority (77%) of dialysis patients were prescribed moderate-intensity statins. The proportions of low- or moderate-intensity statin use were similar, but high-intensity statin use increased from 5.7% in 2013 to 10.5% in 2018. The use of the statin/ezetimibe combination has gradually increased since 2016. Statin use was independently associated with the reduced 1-year all-cause mortality after adjusting for confounding factors (hazard ratio HR 0.89, 95% confidence interval CI 0.80-0.96, P = 0.004).
The prevalence of statin prescriptions in dialysis patients after ASCVD event increased from 2013 to 2018. Most patients received moderate-intensity statin. However, high-intensity statin and statin/ezetimibe combination therapy has remarkably increased. Statin use was associated with decreased 1-year all-cause mortality in dialysis patients with ASCVD.
Statin therapy is essential for secondary prevention in patients with atherosclerotic cardiovascular disease (ASCVD). However, the effects of statin therapy in patients receiving chronic dialysis ...remain uncertain. We aimed to evaluate the effect of statin therapy on long-term mortality in patients on dialysis after a first-time ASCVD. Patients receiving maintenance dialysis aged ≥ 18 years with a first-time ASCVD event between 2013 and 2018 were included in the Korean National Health Insurance Service database. Associations of statin use with long-term mortality were examined using Cox proportional hazards regression models adjusted for demographics and comorbidities. Among 17,242 patients on dialysis, 9611 (55.7%) were prescribed statins after a first-time ASCVD event. Among statin users, 7376 (76.7%) used moderate-intensity statins. During a mean follow-up of 32.6 ± 20.9 months, statin use was associated with a lower risk of all-cause mortality than statin nonuse after adjusting for confounding factors (hazard ratio HR: 0.92; 95% confidence interval CI 0.88-0.97; p = 0.0009). Despite a lack of evidence, more than half of patients on dialysis were prescribed statins after an ASCVD event. In patients on dialysis after ASCVD, statin therapy significantly reduced the risk of long-term all-cause mortality.
Body mass index (BMI), as an important risk factor related to metabolic disease. However, in some studies higher BMI was emphasized as a beneficial factor in the clinical course of patients after ...acute myocardial infarction (AMI) in a concept known as the "BMI paradox." The purpose of this study was to investigate how clinical outcomes of patients treated for AMI differed according to BMI levels. A total of 10,566 patients in the Korea Acute Myocardial Infarction Registry-National Institutes of Health (KAMIR-NIH) from May 2010 to June 2015 were divided into three BMI groups (group 1: BMI < 22 kg/m
, group 2: ≥ 22 and < 26 kg/m
, and group 3: ≥ 26 kg/m
). The primary outcome was major adverse cardiac and cerebrovascular event (MACCE) at 3 years of follow-up. At 1 year of follow-up, the incidence of MACCE in group 1 was 10.1% of that in group 3, with a hazard ratio (HR) of 2.27, and 6.5% in group 2, with an HR of 1.415. This tendency continued up to 3 years of follow-up. The study demonstrated that lower incidence of MACCE in the high BMI group of Asians during the 3-year follow-up period compared to the low BMI group. The results implied higher BMI could exert a positive effect on the long-term clinical outcomes of patients with AMI undergoing percutaneous coronary intervention (PCI).
The available data are not sufficient to understand the clinical impact of statin intensity in elderly patients who undergo percutaneous coronary intervention (PCI) due to acute myocardial infarction ...(AMI).
Using the COREA-AMI registry, we sought to compare the clinical impact of high- versus low-to-moderate-intensity statin in younger (<75 years old) and elderly (≥75 years old) patients. Of 10,719 patients, we included 8,096 patients treated with drug-eluting stents. All patients were classified into high-intensity versus low-to-moderate-intensity statin group according to statin type and dose at discharge. The primary end point was target-vessel failure (TVF), a composite of cardiovascular death, target-vessel MI, or target-lesion revascularization (TLR) from 1 month to 12 months after index PCI.
In younger patients, high-intensity statin showed the better clinical outcomes than low-to-moderate-intensity statin (TVF: 79 5.4% vs. 329 6.8%, adjusted hazard ratio aHR 0.76; 95% confidence interval CI 0.59-0.99; P = 0.038). However, in elderly patients, the incidence rates of the adverse clinical outcomes were similar between two statin-intensity groups (TVF: 38 11.4% vs. 131 10.6%, aHR 1.1; 95% CI 0.76-1.59; P = 0.63).
In this AMI cohort underwent PCI, high-intensity statin showed the better 1-year clinical outcomes than low-to-moderate-intensity statin in younger patients. Meanwhile, the incidence rates of adverse clinical events between high- and low-to-moderate-intensity statin were not statistically different in elderly patients. Further randomized study with large elderly population is warranted.
Background The secondary prevention with pharmacologic therapy is essential for preventing recurrent cardiovascular events in patients experiencing acute myocardial infarction. Guideline-based ...optimal medical therapy (OMT) for patients with acute myocardial infarction consists of antiplatelet therapy, angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers, β-blockers, and statins. We aimed to determine the prescription rate of OMT use at discharge and to evaluate the impact of OMT on long-term clinical outcomes in patients with acute myocardial infarction who underwent percutaneous coronary intervention in the drug-eluting stent era using nationwide cohort data. Methods and Results Using the National Health Insurance claims data in South Korea, patients with acute myocardial infarction who had undergone percutaneous coronary intervention with a drug-eluting stent between July 2013 and June 2017 were enrolled. A total of 35 972 patients were classified into the OMT and non-OMT groups according to the post-percutaneous coronary intervention discharge medication. The primary end point was all-cause death, and the 2 groups were compared using a propensity-score matching analysis. Fifty-seven percent of patients were prescribed OMT at discharge. During the follow-up period (median, 2.0 years interquartile range, 1.1-3.2 years), OMT was associated with a significant reduction in the all-cause mortality (adjusted hazard ratio aHR, 0.82 95% CI, 0.76-0.90;
<0.001) and composite outcome of death or coronary revascularization (aHR, 0.89 95% CI, 0.85-0.93;
<0.001). Conclusions OMT was prescribed at suboptimal rates in South Korea. However, our nationwide cohort study showed that OMT has a benefit for long-term clinical outcomes on all-cause mortality and composite outcome of death or coronary revascularization after percutaneous coronary intervention in the drug-eluting stent era.
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