Magnetic torques generated through spin-orbit coupling
promise energy-efficient spintronic devices. For applications, it is important that these torques switch films with perpendicular magnetizations ...without an external magnetic field
. One suggested approach
to enable such switching uses magnetic trilayers in which the torque on the top magnetic layer can be manipulated by changing the magnetization of the bottom layer. Spin currents generated in the bottom magnetic layer or its interfaces transit the spacer layer and exert a torque on the top magnetization. Here we demonstrate field-free switching in such structures and show that its dependence on the bottom-layer magnetization is not consistent with the anticipated bulk effects
. We describe a mechanism for spin-current generation
at the interface between the bottom layer and the spacer layer, which gives torques that are consistent with the measured magnetization dependence. This other-layer-generated spin-orbit torque is relevant to energy-efficient control of spintronic devices.
Control of magnetization in magnetic nanostructures is essential for development of spintronic devices because it governs fundamental device characteristics such as energy consumption, areal density, ...and operation speed. In this respect, spin–orbit torque (SOT), which originates from the spin–orbit interaction, has been widely investigated due to its efficient manipulation of the magnetization using in‐plane current. SOT spearheads novel spintronic applications including high‐speed magnetic memories, reconfigurable logics, and neuromorphic computing. Herein, recent advances in SOT research, highlighting the considerable benefits and challenges of SOT‐based spintronic devices, are reviewed. First, the materials and structural engineering that enhances SOT efficiency are discussed. Then major experimental results for field‐free SOT switching of perpendicular magnetization are summarized, which includes the introduction of an internal effective magnetic field and the generation of a distinct spin current with out‐of‐plane spin polarization. Finally, advanced SOT functionalities are presented, focusing on the demonstration of reconfigurable and complementary operation in spin logic devices.
Spin–orbit torque (SOT) originating from the spin–orbit coupling has provided significant benefits for spintronic devices such as high‐speed magnetic memories and reconfigurable spin logics because it enables energy‐efficient magnetization switching using in‐plane charge current. Recent progress in SOT research, highlighting the advantages and challenges of SOT‐based spintronic devices is presented.
Microorganisms produce diverse polymers for various purposes such as storing genetic information, energy, and reducing power, and serving as structural materials and scaffolds. Among these polymers, ...polyhydroxyalkanoates (PHAs) are microbial polyesters synthesized and accumulated intracellularly as a storage material of carbon, energy, and reducing power under unfavorable growth conditions in the presence of excess carbon source. PHAs have attracted considerable attention for their wide range of applications in industrial and medical fields. Since the first discovery of PHA accumulating bacteria about 100 years ago, remarkable advances have been made in the understanding of PHA biosynthesis and metabolic engineering of microorganisms toward developing efficient PHA producers. Recently, nonnatural polyesters have also been synthesized by metabolically engineered microorganisms, which opened a new avenue toward sustainable production of more diverse plastics. Herein, the current state of PHAs and nonnatural polyesters is reviewed, covering mechanisms of microbial polyester biosynthesis, metabolic pathways, and enzymes involved in biosynthesis of short‐chain‐length PHAs, medium‐chain‐length PHAs, and nonnatural polyesters, especially 2‐hydroxyacid‐containing polyesters, metabolic engineering strategies to produce novel polymers and enhance production capabilities and fermentation, and downstream processing strategies for cost‐effective production of these microbial polyesters. In addition, the applications of PHAs and prospects are discussed.
Polyhydroxyalkanoates (PHAs) are biodegradable and bio‐based polymers that can substitute petroleum‐based plastics currently in use. A comprehensive overview of the mechanisms and metabolism of PHA biosynthesis, and strategies for strain development, fermentation, and downstream processing toward the cost‐effective production of natural and nonnatural polyesters having diverse material properties is provided. Additionally, applications of PHAs and future prospects are discussed.
Plastics, including poly(ethylene terephthalate) (PET), possess many desirable characteristics and thus are widely used in daily life. However, non-biodegradability, once thought to be an advantage ...offered by plastics, is causing major environmental problem. Recently, a PET-degrading bacterium, Ideonella sakaiensis, was identified and suggested for possible use in degradation and/or recycling of PET. However, the molecular mechanism of PET degradation is not known. Here we report the crystal structure of I. sakaiensis PETase (IsPETase) at 1.5 Å resolution. IsPETase has a Ser-His-Asp catalytic triad at its active site and contains an optimal substrate binding site to accommodate four monohydroxyethyl terephthalate (MHET) moieties of PET. Based on structural and site-directed mutagenesis experiments, the detailed process of PET degradation into MHET, terephthalic acid, and ethylene glycol is suggested. Moreover, other PETase candidates potentially having high PET-degrading activities are suggested based on phylogenetic tree analysis of 69 PETase-like proteins.
Orbital torque in magnetic bilayers Lee, Dongjoon; Go, Dongwook; Park, Hyeon-Jong ...
Nature communications,
11/2021, Letnik:
12, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The orbital Hall effect describes the generation of the orbital current flowing in a perpendicular direction to an external electric field, analogous to the spin Hall effect. As the orbital current ...carries the angular momentum as the spin current does, injection of the orbital current into a ferromagnet can result in torque on the magnetization, which provides a way to detect the orbital Hall effect. With this motivation, we examine the current-induced spin-orbit torques in various ferromagnet/heavy metal bilayers by theory and experiment. Analysis of the magnetic torque reveals the presence of the contribution from the orbital Hall effect in the heavy metal, which competes with the contribution from the spin Hall effect. In particular, we find that the net torque in Ni/Ta bilayers is opposite in sign to the spin Hall theory prediction but instead consistent with the orbital Hall theory, which unambiguously confirms the orbital torque generated by the orbital Hall effect. Our finding opens a possibility of utilizing the orbital current for spintronic device applications, and it will invigorate researches on spin-orbit-coupled phenomena based on orbital engineering.
Ferrimagnetic spintronics Kim, Se Kwon; Beach, Geoffrey S D; Lee, Kyung-Jin ...
Nature materials,
01/2022, Letnik:
21, Številka:
1
Journal Article
Recenzirano
Ferrimagnets composed of multiple and antiferromagnetically coupled magnetic elements have attracted much attention recently as a material platform for spintronics. They offer the combined advantages ...of both ferromagnets and antiferromagnets, namely the easy control and detection of their net magnetization by an external field, antiferromagnetic-like dynamics faster than ferromagnetic dynamics and the potential for high-density devices. This Review summarizes recent progress in ferrimagnetic spintronics, with particular attention to the most-promising functionalities of ferrimagnets, which include their spin transport, spin texture dynamics and all-optical switching.
Antiferromagnetic spin waves have been predicted to offer substantial functionalities for magnonic applications due to the existence of two distinct polarizations, the right-handed and left-handed ...modes, as well as their ultrafast dynamics. However, experimental investigations have been hampered by the field-immunity of antiferromagnets. Ferrimagnets have been shown to be an alternative platform to study antiferromagnetic spin dynamics. Here we investigate thermally excited spin waves in ferrimagnets across the magnetization compensation and angular momentum compensation temperatures using Brillouin light scattering. Our results show that right-handed and left-handed modes intersect at the angular momentum compensation temperature where pure antiferromagnetic spin waves are expected. A field-induced shift of the mode-crossing point from the angular momentum compensation temperature and the gyromagnetic reversal reveal hitherto unrecognized properties of ferrimagnetic dynamics. We also provide a theoretical understanding of our experimental results. Our work demonstrates important aspects of the physics of ferrimagnetic spin waves and opens up the attractive possibility of ferrimagnet-based magnonic devices.
To quantify the impact of the COVID‐19 pandemic and public health interventions on parent and child mental health and family relationships, we examined change in individual and family functioning in ...a sample of parents enrolled in a prevention trial; we examined change before the pandemic (2017–2019) when children were an average of 7 years old to the first months after the imposition of widespread public health interventions in the United States (2020) with paired t tests and HLM models. We examined moderation by parent gender, education, family income, and coparenting conflict. We found large deteriorations from before the pandemic to the first months of the pandemic in child internalizing and externalizing problems and parent depression, and a moderate decline in coparenting quality. Smaller changes were found for parent anxiety and parenting quality. Mothers and families with lower levels of income were at particular risk for deterioration in well‐being. Results indicate a need for widespread family support and intervention to prevent potential family “scarring,” that is, prolonged, intertwined individual mental health and family relationship problems.
Resumen
Para cuantificar el efecto de la pandemia de la COVID‐19 y de las intervenciones de salud pública en la salud mental de los padres y los niños y en las relaciones familiares, analizamos los cambios en el funcionamiento individual y familiar en una muestra de padres inscriptos en un ensayo de prevención; estudiamos el cambio antes de la pandemia (2017‐2019) cuando los niños tenían un promedio de 7 años hasta los primeros meses después de la imposición de las intervenciones generalizadas de salud pública en los Estados Unidos (2020) con pruebas t apareadas y modelos lineales jerárquicos. Analizamos la moderación por género, educación, ingresos familiares y conflicto de cocrianza de los padres. Hallamos grandes deterioros desde antes de la pandemia hasta los primeros meses de la pandemia en problemas de interiorización y exteriorización de los niños y depresión de los padres, y una disminución moderada de la calidad de la cocrianza. También encontramos cambios más pequeños en la ansiedad de los padres y la calidad de la crianza. Las madres y las familias con niveles más bajos de ingresos estuvieron en riesgo particular de deterioro del bienestar. Los resultados indican la necesidad de apoyo familiar generalizado y de intervenciones para prevenir posibles «secuelas» familiares, p. ej.: salud mental individual interconectada y prolongada y problemas en las relaciones familiares.
摘要
本文把COVID‐19和公共健康干预措施对父母和儿童的心理健康以及对家庭关系的影响进行量化，对参加一项预防试验的人群样本进行了研究，主要关于这些受试父母的个体功能和家庭功能产生了哪些变化; 我们采用配对t检验和HLM模型，研究了新冠肺炎(2017‐2019年)前的变化，即平均年龄为7岁的儿童至美国实施广泛公共健康干预措施(2020年)后的第一个月。我们通过父母性别、教育程度、家庭收入和养育子女的冲突来考察这些因素的调适作用。我们发现，儿童对很多问题以及父母的抑郁表现都进行内化和外化，从新冠肺炎流行发生前到新冠大流行的头几个月出现了严重恶化倾向，亲子教育的质量略有下降。父母的焦虑和培养孩子方面的质量也有较小的变化。收入水平较低的母亲和家庭的福祉尤其有恶化的风险。结果表明，需要给予广泛的家庭支持和干预，以防止潜在的家庭"伤疤"，即长期错综搅合在一起的个人心理健康和家庭关系问题。
Spintronic and nanomagnetic devices often derive their functionality from layers of different materials and the interfaces between them. This is especially true for synthetic antiferromagnets - two ...or more ferromagnetic layers that are separated by metallic spacers or tunnel barriers and which have antiparallel magnetizations. Here, we discuss the new opportunities that arise from synthetic antiferromagnets, as compared to crystal antiferromagnets or ferromagnets.
Spintronics relies on magnetization switching through current-induced spin torques. However, because spin transfer torque for ferromagnets is a surface torque, a large switching current is required ...for a thick, thermally stable ferromagnetic cell, and this remains a fundamental obstacle for high-density non-volatile applications with ferromagnets. Here, we report a long spin coherence length and associated bulk-like torque characteristics in an antiferromagnetically coupled ferrimagnetic multilayer. We find that a transverse spin current can pass through >10-nm-thick ferrimagnetic Co/Tb multilayers, whereas it is entirely absorbed by a 1-nm-thick ferromagnetic Co/Ni multilayer. We also find that the switching efficiency of Co/Tb multilayers partially reflects a bulk-like torque characteristic, as it increases with ferrimagnet thickness up to 8 nm and then decreases, in clear contrast to the 1/thickness dependence of ferromagnetic Co/Ni multilayers. Our results on antiferromagnetically coupled systems will invigorate research towards the development of energy-efficient spintronics.
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