Frustrated quantum magnets are expected to host many exotic quantum spin states like quantum spin liquid（QSL）, and have attracted numerous interest in modern condensed matter physics. The discovery of the triangular...Frustrated quantum magnets are expected to host many exotic quantum spin states like quantum spin liquid（QSL）, and have attracted numerous interest in modern condensed matter physics. The discovery of the triangular lattice spin liquid candidate YbMgGaO_4 stimulated an increasing attention on the rare-earth-based frustrated magnets with strong spin-orbit coupling. Here we report the synthesis and characterization of a large family of rare-earth chalcogenides AReCh_2（A = alkali or monovalent ions, Re = rare earth, Ch = O,S,Se）. The family compounds share the same structure（R3 m） as YbMgGaO_4,and antiferromagnetically coupled rare-earth ions form perfect triangular layers that are well separated along the c-axis. Specific heat and magnetic susceptibility measurements on NaYbO_2,NaYbS_2 and NaYbSe_2 single crystals and polycrystals, reveal no structural or magnetic transition down to 50 mK. The family, having the simplest structure and chemical formula among the known QSL candidates, removes the issue on possible exchange disorders in YbMgGaO_4. More excitingly, the rich diversity of the family members allows tunable charge gaps, variable exchange coupling, and many other advantages.This makes the family an ideal platform for fundamental research of QSLs and its promising applications.展开更多
Materials with large spin–orbit torque(SOT)hold considerable significance for many spintronic applications because of their potential for energy-efficient magnetization switching.Unfortunately,most of the existing ma...Materials with large spin–orbit torque(SOT)hold considerable significance for many spintronic applications because of their potential for energy-efficient magnetization switching.Unfortunately,most of the existing materials exhibit an SOT efficiency factor that is much less than unity,requiring a large current for magnetization switching.The search for new materials that can exhibit an SOT efficiency much greater than unity is a topic of active research,and only a few such materials have been identified using conventional approaches.In this paper,we present a machine learning-based approach using a word embedding model that can identify new results by deciphering non-trivial correlations among various items in a specialized scientific text corpus.We show that such a model can be used to identify materials likely to exhibit high SOT and rank them according to their expected SOT strengths.The model captured the essential spintronics knowledge embedded in scientific abstracts within various materials science,physics,and engineering journals and identified 97 new materials to exhibit high SOT.Among them,16 candidate materials are expected to exhibit an SOT efficiency greater than unity,and one of them has recently been confirmed with experiments with quantitative agreement with the model prediction.展开更多
The design of new polynuclear transition metal complexes showing large total spin values through parallel alignment of the spins is an important challenge due to the scarcity of bridging ligands that provide ferromagn...The design of new polynuclear transition metal complexes showing large total spin values through parallel alignment of the spins is an important challenge due to the scarcity of bridging ligands that provide ferromagnetic coupling.Herein,we report two new complexes,a[Mn_(4)^(Ⅱ)Mn_(2)^(Ⅲ)]system containing two non-linear[Mn_(2)^(Ⅱ)Mn^(Ⅲ)]units and a 1D chain system with[Mn_(2)^(Ⅱ)Mn^(Ⅲ)]units that are assembled through dicyanamide bridging ligands coordinated to one of the terminal Mn^(Ⅱ)centers.In both cases,the main exchange interaction is between Mn^(Ⅱ)…Mn^(Ⅲ),showing a relatively strong ferromagnetic coupling.Density functional theory calculations corroborate such ferromagnetic interactions and also provide one magnetostructural correlation,showing that larger Mn^(Ⅱ)-O-Mn^(Ⅲ)angles enhance the strength of the ferromagnetic coupling.Thus,the non-linear[Mn_(2)^(Ⅱ)Mn^(Ⅲ)]units present in these two complexes are specially suited because of their larger Mn^(Ⅱ)-O-Mn^(Ⅲ)angles compared to similar previously reported systems containing a linear[Mn_(2)^(Ⅱ)Mn^(Ⅲ)]unit.展开更多
基金Supported by the Ministry of Science and Technology of China under Grant Nos 2016YFA0300504,2017YFA0302904 and 2016YFA0301001the Natural Science Foundation of China under Grant Nos 11774419,11474357,11822412,11774423 and 11574394
文摘Frustrated quantum magnets are expected to host many exotic quantum spin states like quantum spin liquid（QSL）, and have attracted numerous interest in modern condensed matter physics. The discovery of the triangular lattice spin liquid candidate YbMgGaO_4 stimulated an increasing attention on the rare-earth-based frustrated magnets with strong spin-orbit coupling. Here we report the synthesis and characterization of a large family of rare-earth chalcogenides AReCh_2（A = alkali or monovalent ions, Re = rare earth, Ch = O,S,Se）. The family compounds share the same structure（R3 m） as YbMgGaO_4,and antiferromagnetically coupled rare-earth ions form perfect triangular layers that are well separated along the c-axis. Specific heat and magnetic susceptibility measurements on NaYbO_2,NaYbS_2 and NaYbSe_2 single crystals and polycrystals, reveal no structural or magnetic transition down to 50 mK. The family, having the simplest structure and chemical formula among the known QSL candidates, removes the issue on possible exchange disorders in YbMgGaO_4. More excitingly, the rich diversity of the family members allows tunable charge gaps, variable exchange coupling, and many other advantages.This makes the family an ideal platform for fundamental research of QSLs and its promising applications.
基金supported by Applications and Systems-Driven Center for Energy-Efficient Integrated NanoTechnologies (ASCENT), one of six centers in the Joint University Microelectronics Program (JUMP)a Semiconductor Research Corporation (SRC) program sponsored by Defense Advanced Research Projects Agency (DARPA)in part by the US Department of Energy, under Contract No. DE-AC02-05-CH11231 within the NonEquilibrium Magnetic Materials (NEMM) program.
文摘Materials with large spin–orbit torque(SOT)hold considerable significance for many spintronic applications because of their potential for energy-efficient magnetization switching.Unfortunately,most of the existing materials exhibit an SOT efficiency factor that is much less than unity,requiring a large current for magnetization switching.The search for new materials that can exhibit an SOT efficiency much greater than unity is a topic of active research,and only a few such materials have been identified using conventional approaches.In this paper,we present a machine learning-based approach using a word embedding model that can identify new results by deciphering non-trivial correlations among various items in a specialized scientific text corpus.We show that such a model can be used to identify materials likely to exhibit high SOT and rank them according to their expected SOT strengths.The model captured the essential spintronics knowledge embedded in scientific abstracts within various materials science,physics,and engineering journals and identified 97 new materials to exhibit high SOT.Among them,16 candidate materials are expected to exhibit an SOT efficiency greater than unity,and one of them has recently been confirmed with experiments with quantitative agreement with the model prediction.
基金supported by the Spanish Ministerio de Economía y Competitividad(grant CTQ2015-64579-C3-1-P,MINECO/FEDER,UE)Generalitat de Catalunya for an ICREA Academia award+2 种基金financial support from the Generalitat de Catalunya(7^(th) program Beatriu de Pinos-Marie Curie cofund Fellowship,no.2013 BP-B 00155)the computer resources in the Consorci Serveis Universitaris de Catalunya(CSUC)the National Natural Science Foundation of China(21471066,21390394).
文摘The design of new polynuclear transition metal complexes showing large total spin values through parallel alignment of the spins is an important challenge due to the scarcity of bridging ligands that provide ferromagnetic coupling.Herein,we report two new complexes,a[Mn_(4)^(Ⅱ)Mn_(2)^(Ⅲ)]system containing two non-linear[Mn_(2)^(Ⅱ)Mn^(Ⅲ)]units and a 1D chain system with[Mn_(2)^(Ⅱ)Mn^(Ⅲ)]units that are assembled through dicyanamide bridging ligands coordinated to one of the terminal Mn^(Ⅱ)centers.In both cases,the main exchange interaction is between Mn^(Ⅱ)…Mn^(Ⅲ),showing a relatively strong ferromagnetic coupling.Density functional theory calculations corroborate such ferromagnetic interactions and also provide one magnetostructural correlation,showing that larger Mn^(Ⅱ)-O-Mn^(Ⅲ)angles enhance the strength of the ferromagnetic coupling.Thus,the non-linear[Mn_(2)^(Ⅱ)Mn^(Ⅲ)]units present in these two complexes are specially suited because of their larger Mn^(Ⅱ)-O-Mn^(Ⅲ)angles compared to similar previously reported systems containing a linear[Mn_(2)^(Ⅱ)Mn^(Ⅲ)]unit.
