Antiferromagnet(AFM)/ferromagnet(FM)heterostructure is a popular system for studying the spin–orbit torque(SOT)of AFMs.However,the interfacial exchange bias field induces that the magnetization in FM layer is noncoll...Antiferromagnet(AFM)/ferromagnet(FM)heterostructure is a popular system for studying the spin–orbit torque(SOT)of AFMs.However,the interfacial exchange bias field induces that the magnetization in FM layer is noncollinear to the external magnetic field,namely the magnetic moment drag effect,which further influences the characteristic of SOT efficiency.In this work,we study the SOT efficiencies of IrMn/NiFe bilayers with strong interfacial exchange bias by using spin-torque ferromagnetic resonance(ST-FMR)method.A full analysis on the AFM/FM systems with exchange bias is performed,and the angular dependence of magnetization on external magnetic field is determined through the minimum rule of free energy.The ST-FMR results can be well fitted by this model.We obtained the relative accurate SOT efficiencyξ_(DL)=0.058 for the IrMn film.This work provides a useful method to analyze the angular dependence of ST-FMR results and facilitates the accurate measurement of SOT efficiency for the AFM/FM heterostructures with strong exchange bias.展开更多
Gas turbines play core roles in clean energy supply and the construction of comprehensive energy systems.The control performance of primary frequency modulation of gas turbines has a great impact on the frequency cont...Gas turbines play core roles in clean energy supply and the construction of comprehensive energy systems.The control performance of primary frequency modulation of gas turbines has a great impact on the frequency control of the power grid.However,there are some control difficulties in the primary frequency modulation control of gas turbines,such as the coupling effect of the fuel control loop and speed control loop,slow tracking speed,and so on.To relieve the abovementioned difficulties,a control strategy based on the desired dynamic equation proportional integral(DDE-PI)is proposed in this paper.Based on the parameter stability region,a parameter tuning procedure is summarized.Simulation is carried out to address the ease of use and simplicity of the proposed tuning method.Finally,DDE-PI is applied to the primary frequency modulation system of an MS6001B heavy-duty gas turbine.The simulation results indicate that the gas turbine with the proposed strategy can obtain the best control performance with a strong ability to deal with system uncertainties.The proposed method shows good engineering application potential.展开更多
Three-magnon scattering,a nonlinear process in which a high-energy magnon splits into two low-energy magnons with energy and momentum conservation,has been widely studied in the magnonics community.Here,we report expe...Three-magnon scattering,a nonlinear process in which a high-energy magnon splits into two low-energy magnons with energy and momentum conservation,has been widely studied in the magnonics community.Here,we report experimental observation of nonlinear three-magnon scattering in La_(0.67)Sr_(0.33)MnO_(3)thin films with low magnetic damping(~10^(-4))by all-electric and angle-resolved spin wave spectroscopy.The reflection spectra of the spin wave resonance with high-power excitation at Damon–Eshbach configuration demonstrate a scattering regime with gradual signal disappearance,where a magnon of Damon–Eshbach mode decays into two magnons of volume mode above the threshold power(-10 dBm)of the injected microwave.The nonlinear scattering is only allowed at low-field regime and the calculated dispersions of dipole-exchange spin wave claim the mechanism of allowed and forbidden three-magnon scattering.The films and heterostructures of La_(0.67)Sr_(0.33)MnO_(3)have been already demonstrated with rich physical phenomena and great versatility,in this work the nonlinear magnetic dynamics of La_(0.67)Sr_(0.33)MnO_(3)thin films is revealed,which offer more possibility for applications to oxide magnonics and nonlinear magnonic devices.展开更多
Magnetic orderings, i.e., the spontaneous alignment of electron spins below a critical temperature, have been playing key roles in modern science and technologies for both the wide applications of magnetic recording f...Magnetic orderings, i.e., the spontaneous alignment of electron spins below a critical temperature, have been playing key roles in modern science and technologies for both the wide applications of magnetic recording for information storage and the vibrant potential of solid state electronic spin devices (also known as spintronics) for logic operations. In the past decades, thanks to the development of thin film technologies, magnetic thin films via sputtering or epitaxial growth have made the spintronic devices possible at the industrial scale. Yet thinner materials at lower costs with more versatile functionalities are highly desirable for advancing future spintronics. Recently, van der Waals magnetic materials, a family of magnets that can in principle be exfoliated down to the monolayer limit, seem to have brought tremendous opportunities: new generation van der Waals spintronic devices can be seamlessly assembled with possible applications such as optoelectronics, flexible electronics, and etc. Moreover, those exfoliated spintronic devices can potentially be compatible with the famed metal-oxide field effect transistor architectures, allowing the harness of spin performances through the knob of an electrostatic field.展开更多
Magnetic two-dimensional(2D)van derWaals(vdWs)materials and their heterostructures attract increasing attention in the spintronics community due to their various degrees of freedom such as spin,charge,and energy valle...Magnetic two-dimensional(2D)van derWaals(vdWs)materials and their heterostructures attract increasing attention in the spintronics community due to their various degrees of freedom such as spin,charge,and energy valley,which may stimulate potential applications in the field of low-power and high-speed spintronic devices in the future.This review begins with introducing the long-range magnetic order in 2D vdWs materials and the recent progress of tunning their properties by electrostatic doping and stress.Next,the proximity-effect,current-induced magnetization switching,and the related spintronic devices(such as magnetic tunnel junctions and spin valves)based on magnetic 2D vdWs materials are presented.Finally,the development trend of magnetic 2D vdWs materials is discussed.This review provides comprehensive understandings for the development of novel spintronic applications based on magnetic 2D vdWs materials.展开更多
The binary alloy/ferromagnetic metal heterostructure has drawn extensive attention in the research field of spin–orbittorque(SOT)due to the potential enhancement of SOT efficiency via composition engineering.In this ...The binary alloy/ferromagnetic metal heterostructure has drawn extensive attention in the research field of spin–orbittorque(SOT)due to the potential enhancement of SOT efficiency via composition engineering.In this work,the magneticproperties and SOT efficiency in the Pt100−xNix/Ni78Fe22 bilayers were investigated via the spin-torque ferromagneticresonance(ST-FMR)technique.The effective magnetic anisotropy field and effective damping constant extracted by analyzing the ST-FMR spectra show a weak dependence on the Ni concentration.The effective spin-mixing conductanceof 8.40×10^(14)Ω−1·m−2and the interfacial spin transparency Tin of 0.59 were obtained for the sample of Pt70Ni30/NiFebilayer.More interestingly,the SOT efficiency that is carefully extracted from the angular dependence of ST-FMR spectrashows a nonmonotonic dependence on the Ni concentration,which reaches the maximum at x=18.The enhancement ofthe SOT efficiency by alloying the Ni with Pt shows potential in lowering the critical switching current.Moreover,alloyingrelatively cheaper Ni with Pt may promote to reduce the cost of SOT devices.展开更多
Detection of ultralow magnetic field requires magnetic sensors with high sensitivity and low noise level,especially for low operating frequency applications.We investigated the transport properties of tunnel magnetore...Detection of ultralow magnetic field requires magnetic sensors with high sensitivity and low noise level,especially for low operating frequency applications.We investigated the transport properties of tunnel magnetoresistance(TMR)sensors based on the double indirect exchange coupling effect.The TMR ratio of about 150%was obtained in the magnetic tunnel junctions and linear response to an in-plane magnetic field was successfully achieved.A high sensitivity of 1.85%/Oe was achieved due to a designed soft pinned sensing layer of CoFeB/NiFe/Ru/IrMn.Furthermore,the voltage output sensitivity and the noise level of 10.7 mV/V/Oe,10 nT/Hz^(1/2)at 1 Hz and3.3 nT/Hz^(1/2)at 10 Hz were achieved in Full Wheatstone Bridge configuration.This kind of magnetic sensors can be used in the field of smart grid for current detection and sensing.展开更多
Beowulf, national epic of the Anglo-Saxon people, sings high praise of the ancient hero Beowulf who represents the ideal warrior and king. Sir Gawain, a medieval knight presented in the poem Sir Gawain and the Green K...Beowulf, national epic of the Anglo-Saxon people, sings high praise of the ancient hero Beowulf who represents the ideal warrior and king. Sir Gawain, a medieval knight presented in the poem Sir Gawain and the Green Knight, is also described as a hero and a model knight. This paper is to find out the main features of the English heroes by comparing the two heroes.展开更多
Exploiting the valley degrees of freedom as information carriers provides new opportunities for the development of valleytronics.Monolayer transition metal dichalcogenides(TMDs)with broken space-inversion symmetry exh...Exploiting the valley degrees of freedom as information carriers provides new opportunities for the development of valleytronics.Monolayer transition metal dichalcogenides(TMDs)with broken space-inversion symmetry exhibit emerging valley pseudospins,making them ideal platforms for studying valley electronics.However,intervalley scattering of different energy valleys limits the achievable degree of valley polarization.Here,we constructed WSe_(2)/yttrium iron garnet(YIG)heterostructures and demonstrated that the interfacial magnetic exchange effect on the YIG magnetic substrate can enhance valley polarization by up to 63%,significantly higher than that of a monolayer WSe_(2)on SiO_(2)/Si(11%).Additionally,multiple sharp exciton peaks appear in the WSe_(2)/YIG heterostructures due to the strong magnetic proximity effect at the magnetic-substrate interface that enhances exciton emission efficiency.Moreover,under the effect of external magnetic field,the magnetic direction of the magnetic substrate enhances valley polarization,further demonstrating that the magnetic proximity effect regulates valley polarization.Our results provide a new way to regulate valley polarization and demonstrate the promising application of magnetic heterojunctions in magneto-optoelectronics.展开更多
Soil conservation is necessary to achieve a sustainable world because soils play a crucial role in the Earth's system.At the same time,the applicable and precise methods are vital to obtaining credible data in soi...Soil conservation is necessary to achieve a sustainable world because soils play a crucial role in the Earth's system.At the same time,the applicable and precise methods are vital to obtaining credible data in soil studies.A collection of 10 articles have been organized to focus on the new technologies regarding soil conservation and eco-sustainability and the results related to the novel approaches.The articles put effort into the innovative works of field investigations,field experiments,model experiments,and nu-merical simulations.Pivotal questions baffling soil scientists have been clarified and solved,and many valuable insights have been aroused.展开更多
Although many emerging new phenomena have been unraveled in two dimensional(2D)materials with long-range spin orderings,the usually low critical temperature in van der Waals(vdW)magnetic material has thus far hindered...Although many emerging new phenomena have been unraveled in two dimensional(2D)materials with long-range spin orderings,the usually low critical temperature in van der Waals(vdW)magnetic material has thus far hindered the related practical applications.Here,we show that ferromagnetism can hold above 300 K in a metallic phase of 1T-CrTe2 down to the ultra-thin limit.It thus makes CrTe2 so far the only known exfoliated ultra-thin vdW magnets with intrinsic long-range magnetic ordering above room temperature.An in-plane room-temperature negative anisotropic magnetoresistance(AMR)was obtained in ultra-thin CrTe2 devices,with a sign change in the AMR at lower temperature,with−0.6%and+5%at 300 and 10 K,respectively.Our findings provide insights into magnetism in ultra-thin CrTe2,expanding the vdW crystals toolbox for future room-temperature spintronic applications.展开更多
Voltage control of magnetism promises great energy efficiency in writing magnetic memory. Here, using Cr/Mo/CoFeB/MgO multilayers stable under high annealing temperatures up to 590°C, we significantly enhance the...Voltage control of magnetism promises great energy efficiency in writing magnetic memory. Here, using Cr/Mo/CoFeB/MgO multilayers stable under high annealing temperatures up to 590°C, we significantly enhance the interfacial crystallinity, thereby the interface-originated perpendicular magnetic anisotropy(PMA), voltage-controlled magnetic anisotropy(VCMA), and interface magnetoelectric(ME) effect. High interfacial PMA of 1.35 mJ/m^2, VCMA coefficient of-138 fJ/(V m), and interface ME coefficient, which is 2-3 orders of magnitude larger than ab initio calculation results are simultaneously achieved after annealing at 500°C. These promising results enabled by the industry-applicable sputtering process will pave the way for highdensity voltage-controlled spintronic devices.展开更多
All-electrical driven magnetization switching attracts much attention in next-generation spintronic memory and logic devices,particularly in magnetic random-access memory(MRAM)based on the spin–orbit torque(SOT),i.e....All-electrical driven magnetization switching attracts much attention in next-generation spintronic memory and logic devices,particularly in magnetic random-access memory(MRAM)based on the spin–orbit torque(SOT),i.e.SOT-MRAM,due to its advantages of low power consumption,fast write/read speed,and improved endurance,etc.For conventional SOT-driven switching of the magnet with perpendicular magnetic anisotropy,an external assisted magnetic field is necessary to break the inversion symmetry of the magnet,which not only induces the additional power consumption but also makes the circuit more complicated.Over the last decade,significant effort has been devoted to field-free magnetization manipulation by using SOT.In this review,we introduce the basic concepts of SOT.After that,we mainly focus on several approaches to realize the field-free deterministic SOT switching of the perpendicular magnet.The mechanisms mainly include mirror symmetry breaking,chiral symmetry breaking,exchange bias,and interlayer exchange coupling.Furthermore,we show the recent progress in the study of SOT with unconventional origin and symmetry.The final section is devoted to the industrial-level approach for potential applications of field-free SOT switching in SOT-MRAM technology.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFB3601300)the National Natural Science Foundation of China(Grant Nos.52201290,12074158,and 12174166)the Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2022-kb01)。
文摘Antiferromagnet(AFM)/ferromagnet(FM)heterostructure is a popular system for studying the spin–orbit torque(SOT)of AFMs.However,the interfacial exchange bias field induces that the magnetization in FM layer is noncollinear to the external magnetic field,namely the magnetic moment drag effect,which further influences the characteristic of SOT efficiency.In this work,we study the SOT efficiencies of IrMn/NiFe bilayers with strong interfacial exchange bias by using spin-torque ferromagnetic resonance(ST-FMR)method.A full analysis on the AFM/FM systems with exchange bias is performed,and the angular dependence of magnetization on external magnetic field is determined through the minimum rule of free energy.The ST-FMR results can be well fitted by this model.We obtained the relative accurate SOT efficiencyξ_(DL)=0.058 for the IrMn film.This work provides a useful method to analyze the angular dependence of ST-FMR results and facilitates the accurate measurement of SOT efficiency for the AFM/FM heterostructures with strong exchange bias.
基金supported by Science and Technology Project of Jiangsu Frontier Electric Technology Co.,Ltd. (Grant Number KJ202004),Gao A.M. (author who received the grant).
文摘Gas turbines play core roles in clean energy supply and the construction of comprehensive energy systems.The control performance of primary frequency modulation of gas turbines has a great impact on the frequency control of the power grid.However,there are some control difficulties in the primary frequency modulation control of gas turbines,such as the coupling effect of the fuel control loop and speed control loop,slow tracking speed,and so on.To relieve the abovementioned difficulties,a control strategy based on the desired dynamic equation proportional integral(DDE-PI)is proposed in this paper.Based on the parameter stability region,a parameter tuning procedure is summarized.Simulation is carried out to address the ease of use and simplicity of the proposed tuning method.Finally,DDE-PI is applied to the primary frequency modulation system of an MS6001B heavy-duty gas turbine.The simulation results indicate that the gas turbine with the proposed strategy can obtain the best control performance with a strong ability to deal with system uncertainties.The proposed method shows good engineering application potential.
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFA1402801)the support from the China Post-doctoral Science Foundation Funded Project(Grant No.2021M700344)+1 种基金by the National Natural Science Foundation of China(Grant Nos.12074026,12104208,and U1801661)the support from the Academic Excellence Foundation of BUAA for PhD Students。
文摘Three-magnon scattering,a nonlinear process in which a high-energy magnon splits into two low-energy magnons with energy and momentum conservation,has been widely studied in the magnonics community.Here,we report experimental observation of nonlinear three-magnon scattering in La_(0.67)Sr_(0.33)MnO_(3)thin films with low magnetic damping(~10^(-4))by all-electric and angle-resolved spin wave spectroscopy.The reflection spectra of the spin wave resonance with high-power excitation at Damon–Eshbach configuration demonstrate a scattering regime with gradual signal disappearance,where a magnon of Damon–Eshbach mode decays into two magnons of volume mode above the threshold power(-10 dBm)of the injected microwave.The nonlinear scattering is only allowed at low-field regime and the calculated dispersions of dipole-exchange spin wave claim the mechanism of allowed and forbidden three-magnon scattering.The films and heterostructures of La_(0.67)Sr_(0.33)MnO_(3)have been already demonstrated with rich physical phenomena and great versatility,in this work the nonlinear magnetic dynamics of La_(0.67)Sr_(0.33)MnO_(3)thin films is revealed,which offer more possibility for applications to oxide magnonics and nonlinear magnonic devices.
基金supported by the National Key R&D Program of China (No. 2017YFA0206302)supported by the National Natural Science Foundation of China (Grants No. 51627801)+1 种基金the finical supports from the National Natural Science Foundation of China (Grants No. 11874409)supports from the Major Program of Aerospace Advanced Manufacturing Technology Research Foundation NSFC and CASC,China (No. U1537204)
文摘Magnetic orderings, i.e., the spontaneous alignment of electron spins below a critical temperature, have been playing key roles in modern science and technologies for both the wide applications of magnetic recording for information storage and the vibrant potential of solid state electronic spin devices (also known as spintronics) for logic operations. In the past decades, thanks to the development of thin film technologies, magnetic thin films via sputtering or epitaxial growth have made the spintronic devices possible at the industrial scale. Yet thinner materials at lower costs with more versatile functionalities are highly desirable for advancing future spintronics. Recently, van der Waals magnetic materials, a family of magnets that can in principle be exfoliated down to the monolayer limit, seem to have brought tremendous opportunities: new generation van der Waals spintronic devices can be seamlessly assembled with possible applications such as optoelectronics, flexible electronics, and etc. Moreover, those exfoliated spintronic devices can potentially be compatible with the famed metal-oxide field effect transistor architectures, allowing the harness of spin performances through the knob of an electrostatic field.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0206200)the National Natural Science Foundation of China(Grant No.11874409)+2 种基金the Beijing Natural Science Foundation,China(Grant No.Z190009)the Science Center of the National Science Foundation of China(Grant No.52088101)the K.C.Wong Education Foundation(Grant No.GJTD-2019-14).
文摘Magnetic two-dimensional(2D)van derWaals(vdWs)materials and their heterostructures attract increasing attention in the spintronics community due to their various degrees of freedom such as spin,charge,and energy valley,which may stimulate potential applications in the field of low-power and high-speed spintronic devices in the future.This review begins with introducing the long-range magnetic order in 2D vdWs materials and the recent progress of tunning their properties by electrostatic doping and stress.Next,the proximity-effect,current-induced magnetization switching,and the related spintronic devices(such as magnetic tunnel junctions and spin valves)based on magnetic 2D vdWs materials are presented.Finally,the development trend of magnetic 2D vdWs materials is discussed.This review provides comprehensive understandings for the development of novel spintronic applications based on magnetic 2D vdWs materials.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51901025 and 51625101)the Fundamental Research Funds for the CentralUniversities,China(Grant No.310421101)the Beijing Natural Science Foundation,China(Grant No.Z190007).
文摘The binary alloy/ferromagnetic metal heterostructure has drawn extensive attention in the research field of spin–orbittorque(SOT)due to the potential enhancement of SOT efficiency via composition engineering.In this work,the magneticproperties and SOT efficiency in the Pt100−xNix/Ni78Fe22 bilayers were investigated via the spin-torque ferromagneticresonance(ST-FMR)technique.The effective magnetic anisotropy field and effective damping constant extracted by analyzing the ST-FMR spectra show a weak dependence on the Ni concentration.The effective spin-mixing conductanceof 8.40×10^(14)Ω−1·m−2and the interfacial spin transparency Tin of 0.59 were obtained for the sample of Pt70Ni30/NiFebilayer.More interestingly,the SOT efficiency that is carefully extracted from the angular dependence of ST-FMR spectrashows a nonmonotonic dependence on the Ni concentration,which reaches the maximum at x=18.The enhancement ofthe SOT efficiency by alloying the Ni with Pt shows potential in lowering the critical switching current.Moreover,alloyingrelatively cheaper Ni with Pt may promote to reduce the cost of SOT devices.
基金Supported by the Framework Project of SGCC(Grant No.5700-202058381A-0-0-00)the National Key Research and Development Program of China(Grant No.2017YFA0206200)。
文摘Detection of ultralow magnetic field requires magnetic sensors with high sensitivity and low noise level,especially for low operating frequency applications.We investigated the transport properties of tunnel magnetoresistance(TMR)sensors based on the double indirect exchange coupling effect.The TMR ratio of about 150%was obtained in the magnetic tunnel junctions and linear response to an in-plane magnetic field was successfully achieved.A high sensitivity of 1.85%/Oe was achieved due to a designed soft pinned sensing layer of CoFeB/NiFe/Ru/IrMn.Furthermore,the voltage output sensitivity and the noise level of 10.7 mV/V/Oe,10 nT/Hz^(1/2)at 1 Hz and3.3 nT/Hz^(1/2)at 10 Hz were achieved in Full Wheatstone Bridge configuration.This kind of magnetic sensors can be used in the field of smart grid for current detection and sensing.
文摘Beowulf, national epic of the Anglo-Saxon people, sings high praise of the ancient hero Beowulf who represents the ideal warrior and king. Sir Gawain, a medieval knight presented in the poem Sir Gawain and the Green Knight, is also described as a hero and a model knight. This paper is to find out the main features of the English heroes by comparing the two heroes.
基金The authors would like to acknowledge the National Natural Science Foundation of China(Nos.61775241,62090035,and U19A2090)the Hunan Province Key Research and Development Project(No.2019GK2233)+8 种基金the Hunan Provincial Science Fund for Distinguished Young Scholars(No.2020JJ2059)the Youth Innovation Team of CSU(No.2019012)the Key Program of Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)the Postdoctoral Science Foundation of China(No.2022M713546)The authors would also like to express their gratitude to the High-Performance Complex Manufacturing Key State Lab Project,Central South University(No.ZZYJKT2020-12)the Australian Research Council(ARC)Discovery Project(No.DP180102976)for their support of Z.W.L.C.T.W.acknowledges support from the National Natural Science Foundation of China(No.11974387)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB33000000)H.H.Z.is grateful for the support from the Postdoctoral Science Foundation of China(No.2022M713546).
文摘Exploiting the valley degrees of freedom as information carriers provides new opportunities for the development of valleytronics.Monolayer transition metal dichalcogenides(TMDs)with broken space-inversion symmetry exhibit emerging valley pseudospins,making them ideal platforms for studying valley electronics.However,intervalley scattering of different energy valleys limits the achievable degree of valley polarization.Here,we constructed WSe_(2)/yttrium iron garnet(YIG)heterostructures and demonstrated that the interfacial magnetic exchange effect on the YIG magnetic substrate can enhance valley polarization by up to 63%,significantly higher than that of a monolayer WSe_(2)on SiO_(2)/Si(11%).Additionally,multiple sharp exciton peaks appear in the WSe_(2)/YIG heterostructures due to the strong magnetic proximity effect at the magnetic-substrate interface that enhances exciton emission efficiency.Moreover,under the effect of external magnetic field,the magnetic direction of the magnetic substrate enhances valley polarization,further demonstrating that the magnetic proximity effect regulates valley polarization.Our results provide a new way to regulate valley polarization and demonstrate the promising application of magnetic heterojunctions in magneto-optoelectronics.
基金The special issue is finacially supported by the National Natural Science Foundation of China(51879032).
文摘Soil conservation is necessary to achieve a sustainable world because soils play a crucial role in the Earth's system.At the same time,the applicable and precise methods are vital to obtaining credible data in soil studies.A collection of 10 articles have been organized to focus on the new technologies regarding soil conservation and eco-sustainability and the results related to the novel approaches.The articles put effort into the innovative works of field investigations,field experiments,model experiments,and nu-merical simulations.Pivotal questions baffling soil scientists have been clarified and solved,and many valuable insights have been aroused.
基金This work is supported by the National Key R&D Program of China(Nos.2019YFA0307800,2017YFA0206302,and 2017YFA0206200)the National Natural Science Foundation of China(NSFC)(Nos.11974357,U1932151,and 51627801)+4 种基金G.Y.and X.H.thank the financial supports from the National Natural Science Foundation of China(NSFC)(No.11874409)This work is supported by the National Natural Science Foundation of China(NSFC)(Nos.61574060,and 8206300210)T.Y.acknowledges supports from the Major Program of Aerospace Advanced Manufacturing Technology Research Foundation NSFC and CASC,China(No.U1537204)Z.H.acknowledges the support from the Program of State Key Laboratory of Quantum Optics and Quantum Optics Devices(No.KF201816)The authors appreciate the help of Dr.Binbin Jiang in obtaining the HAADF-STEM images.
文摘Although many emerging new phenomena have been unraveled in two dimensional(2D)materials with long-range spin orderings,the usually low critical temperature in van der Waals(vdW)magnetic material has thus far hindered the related practical applications.Here,we show that ferromagnetism can hold above 300 K in a metallic phase of 1T-CrTe2 down to the ultra-thin limit.It thus makes CrTe2 so far the only known exfoliated ultra-thin vdW magnets with intrinsic long-range magnetic ordering above room temperature.An in-plane room-temperature negative anisotropic magnetoresistance(AMR)was obtained in ultra-thin CrTe2 devices,with a sign change in the AMR at lower temperature,with−0.6%and+5%at 300 and 10 K,respectively.Our findings provide insights into magnetism in ultra-thin CrTe2,expanding the vdW crystals toolbox for future room-temperature spintronic applications.
基金supported by the NSF Nanosystems Engineering Research Center for Translational Applications of Nanoscale Multiferroic Systems (TANMS)a Phase II NSF Small Business Innovation Research award+1 种基金supported by the Energy Frontier Research Center for Spins and Heat in Nanoscale Electronic Systems (SHINES)support of China Scholarship Council (CSC)
文摘Voltage control of magnetism promises great energy efficiency in writing magnetic memory. Here, using Cr/Mo/CoFeB/MgO multilayers stable under high annealing temperatures up to 590°C, we significantly enhance the interfacial crystallinity, thereby the interface-originated perpendicular magnetic anisotropy(PMA), voltage-controlled magnetic anisotropy(VCMA), and interface magnetoelectric(ME) effect. High interfacial PMA of 1.35 mJ/m^2, VCMA coefficient of-138 fJ/(V m), and interface ME coefficient, which is 2-3 orders of magnitude larger than ab initio calculation results are simultaneously achieved after annealing at 500°C. These promising results enabled by the industry-applicable sputtering process will pave the way for highdensity voltage-controlled spintronic devices.
基金This work was supported by start-up funding support from Songshan Lake Materials Laboratory(Y1D1071S511)NSF Award Nos.1935362,1909416,1810163 and 1611570,the U.S.Army Research Office MURI program under Grant Nos.W911NF-16-1-0472WN911NF-20-2-0166,and the National Key Technologies R&D Program of China(Nos.2016YFA0201102 and 2017YFA0206200).
文摘All-electrical driven magnetization switching attracts much attention in next-generation spintronic memory and logic devices,particularly in magnetic random-access memory(MRAM)based on the spin–orbit torque(SOT),i.e.SOT-MRAM,due to its advantages of low power consumption,fast write/read speed,and improved endurance,etc.For conventional SOT-driven switching of the magnet with perpendicular magnetic anisotropy,an external assisted magnetic field is necessary to break the inversion symmetry of the magnet,which not only induces the additional power consumption but also makes the circuit more complicated.Over the last decade,significant effort has been devoted to field-free magnetization manipulation by using SOT.In this review,we introduce the basic concepts of SOT.After that,we mainly focus on several approaches to realize the field-free deterministic SOT switching of the perpendicular magnet.The mechanisms mainly include mirror symmetry breaking,chiral symmetry breaking,exchange bias,and interlayer exchange coupling.Furthermore,we show the recent progress in the study of SOT with unconventional origin and symmetry.The final section is devoted to the industrial-level approach for potential applications of field-free SOT switching in SOT-MRAM technology.