Field-free spin-orbit torque(SOT)switching of perpendicular magnetization is essential for future spintronic devices.This study demonstrates the field-free switching of perpendicular magnetization in an HfO_(2)/Pt/Co/...Field-free spin-orbit torque(SOT)switching of perpendicular magnetization is essential for future spintronic devices.This study demonstrates the field-free switching of perpendicular magnetization in an HfO_(2)/Pt/Co/TaO_(x) structure,which is facilitated by a wedge-shaped HfO_(2)buffer layer.The field-free switching ratio varies with HfO_(2)thickness,reaching optimal performance at 25 nm.This phenomenon is attributed to the lateral anisotropy gradient of the Co layer,which is induced by the wedge-shaped HfO_(2)buffer layer.The thickness gradient of HfO_(2)along the wedge creates a corresponding lateral anisotropy gradient in the Co layer,correlating with the switching ratio.These findings indicate that field-free SOT switching can be achieved through designing buffer layer,offering a novel approach to innovating spin-orbit device.展开更多
Topological magnetism with strong robustness,nanoscale dimensions and ultralow driving current density(106 A/m^(2))is promising for applications in information sensing,storage,and processing,and thus sparking widespre...Topological magnetism with strong robustness,nanoscale dimensions and ultralow driving current density(106 A/m^(2))is promising for applications in information sensing,storage,and processing,and thus sparking widespread research interest.Exploring candidate material systems with nanoscale size and easily tunable properties is a key for realizing practical topological magnetism-based spintronic devices.Here,we propose a class of ultrathin heterostructures,Fe/Bi_(2)O_(2)X(X=S,Se,Te)by deposing metal Fe on quasi-two-dimensional(2D)bismuth oxychalcogenides Bi_(2)O_(2)X(X=S,Se,Te)with excellent ferroelectric/ferroelastic properties.Large Dzyaloshinskii–Moriya interaction(DMI)and topological magnetism can be realized.Our atomistic spin dynamics simulations demonstrate that field-free vortex–antivortex loops and sub-10 nm skyrmions exist in Fe/Bi_(2)O_(2)S and Fe/Bi_(2)O_(2)Se interfaces,respectively.These results provide a possible strategy to tailor topological magnetism in ultrathin magnets/2D materials interfaces,which is extremely vital for spintronics applications.展开更多
This paper studies the molecular rotational excitation and field-free spatial alignment in a nonresonant intense laser field numerically and analytically by using the time-dependent SchrSdinger equation. The broad rot...This paper studies the molecular rotational excitation and field-free spatial alignment in a nonresonant intense laser field numerically and analytically by using the time-dependent SchrSdinger equation. The broad rotational wave packets excited by the femtosecond pulse are defined in conjugate angle space, and their coefficients are obtained by solving a set of coupled linear equations. Both single molecule orientation angles and an ensemble of O2 and CO molecule angular distributions are calculated in detail. The numerical results show that, for single molecule highest occupied molecular orbital （HOMO） symmetry σ tends to have a molecular orientation along the laser polarization direction and the permanent dipole moment diminishes the mean of the orientation angles; for an ensemble of molecules, angular distributions provide more complex and additional information at times where there are no revivals in the single molecule plot. In particular, at the revival peak instant, with the increase of temperature of the molecular ensemble, the anisotropic angular distributions with respect to the laser polarization direction of the πg orbital gradually transform to the symmetrical distributions regarding the laser polarization vector and for two HOMO configurations angular distributions of all directions are confined within a smaller angle when the temperature of the molecular ensemble is higher.展开更多
Through theoretical analysis,we show how aligning pulse durations affect the degree and the time-rate slope of nitrogen field-free alignment at a fixed pulse intensity.It is found that both the degree and the slope fi...Through theoretical analysis,we show how aligning pulse durations affect the degree and the time-rate slope of nitrogen field-free alignment at a fixed pulse intensity.It is found that both the degree and the slope first increase,then saturate,and finally decrease with the increasing pump duration.The optimal durations for the maximum degree and the maximum slope of the alignment are found to be different.Additionally,they are found to mainly depend on the molecular rotational period,and are affected by the temperature and the aligning pump intensities.The mechanism of molecular alignment is also discussed.展开更多
Current induced spin-orbit torque(SOT)switching of magnetization is a promising technology for nonvolatile spintronic memory and logic applications.In this work,we systematically investigated the effect of Ta thicknes...Current induced spin-orbit torque(SOT)switching of magnetization is a promising technology for nonvolatile spintronic memory and logic applications.In this work,we systematically investigated the effect of Ta thickness on the magnetic properties,field-free switching and SOT efficiency in a ferromagnetically coupled Co/Ta/Co Fe B trilayer with perpendicular magnetic anisotropy.We found that both the anisotropy field and coercivity increase with increasing Ta thickness from0.15 nm to 0.4 nm.With further increase of Ta thickness to 0.5 nm,two-step switching is observed,indicating that the two magnetic layers are magnetically decoupled.Measurements of pulse-current induced magnetization switching and harmonic Hall voltages show that the critical switching current density increases while the field-free switching ratio and SOT efficiency decrease with increasing Ta thickness.Both the enhanced spin memory loss and reduced interlayer exchange coupling might be responsible for theβ_(DL)decrease as the Ta spacer thickness increases.The studied structure with the incorporation of a Co Fe B layer is able to realize field-free switching in the strong ferromagnetic coupling region,which may contribute to the further development of magnetic tunnel junctions for better memory applications.展开更多
L1_(0)-FePt distinguishes itself for its ultrahigh perpendicular magnetic anisotropy(PMA),enabling thermally stabile memory cells to scale down to 3 nm.The recently discovered“bulk”spin−orbit torques in L1_(0)-FePt ...L1_(0)-FePt distinguishes itself for its ultrahigh perpendicular magnetic anisotropy(PMA),enabling thermally stabile memory cells to scale down to 3 nm.The recently discovered“bulk”spin−orbit torques in L1_(0)-FePt provide an efficient and scalable way to manipulate the L1_(0)-FePt magnetization.However,the existence of an external field during the switching limits its practical application,and therefore field-free switching of L1_(0)-FePt is highly demanded.In this manuscript,by growing the L1_(0)-FePt film on vicinal MgO(001)substrates,we realize the field-free switching of L1_(0)-FePt.This method is different from previously established strategies as it does not need to add other functional layers or create asymmetry in the film structure.The dependence on the vicinal angle,film thickness,and growth temperature demonstrates a wide operation window for the fieldfree switching of L1_(0)-FePt.We confirm the physical origin of the field-free switching is due to the tilted anisotropy of L1_(0)-FePt induced by the vicinal surface.We also quantitatively characterize the spin-orbit torques in the L1_(0)-FePt films.Our results extend beyond the established strategies to realize field-free switching,and potentially could be applied to mass production.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
Magnetoresistive random access memory(MRAM)is a promising non-volatile memory technology that can be utilized as an energy and space-efficient storage and computing solution,particularly in cache functions within circ...Magnetoresistive random access memory(MRAM)is a promising non-volatile memory technology that can be utilized as an energy and space-efficient storage and computing solution,particularly in cache functions within circuits.Although MRAM has achieved mass production,its manufacturing process still remains challenging,resulting in only a few semiconductor companies dominating its production.In this review,we delve into the materials,processes,and devices used in MRAM,focusing on both the widely adopted spin transfer torque MRAM and the next-generation spin-orbit torque MRAM.We provide an overview of their operational mechanisms and manufacturing technologies.Furthermore,we outline the major hurdles faced in MRAM manufacturing and propose potential solutions in detail.Then,the applications of MRAM in artificial intelligent hardware are introduced.Finally,we present an outlook on the future development and applications of MRAM.展开更多
为探究脱病毒种苗对果蔗的影响,本研究以广东黄皮果蔗为试验材料,进行了自留种、脱毒一代、脱毒二代果蔗种苗的田间性状和果汁品质的比较研究。结果表明,3种材料中,脱毒二代果蔗的田间生长状态最佳,与自留种和脱毒一代相比,其地上株高...为探究脱病毒种苗对果蔗的影响,本研究以广东黄皮果蔗为试验材料,进行了自留种、脱毒一代、脱毒二代果蔗种苗的田间性状和果汁品质的比较研究。结果表明,3种材料中,脱毒二代果蔗的田间生长状态最佳,与自留种和脱毒一代相比,其地上株高分别提高9.08%、5.80%(其中可食部分高度分别提高13.64%、7.19%),茎粗分别提高13.98%、9.71%,产量分别提高47.76%、63.72%(达到159.5 t hm^(-2)),出汁率分别提高3.64%、9.17%,蔗汁的总糖含量分别下降10.14%、12.73%;脱毒对果蔗蔗汁的密度、锤度和纤维含量无显著影响;脱毒苗第一代果蔗与自留种的产量和蔗汁品质无显著差异,脱毒组培苗作为第一代种苗可用于繁育脱毒果蔗种茎,3—4月份适宜移栽。因此,相对于一代组培苗,采用脱毒第二代种苗(脱毒第一代种苗种植收获的果蔗种茎)进行商品蔗种植效果更好,可促进果蔗田间生长,显著提高果蔗的产量。展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.12274108)the Natural Science Foundation of Zhejiang Province,China (Grant Nos.LY23A040008 and LY23A040008)the Basic Scientific Research Project of Wenzhou,China (Grant No.G20220025)。
文摘Field-free spin-orbit torque(SOT)switching of perpendicular magnetization is essential for future spintronic devices.This study demonstrates the field-free switching of perpendicular magnetization in an HfO_(2)/Pt/Co/TaO_(x) structure,which is facilitated by a wedge-shaped HfO_(2)buffer layer.The field-free switching ratio varies with HfO_(2)thickness,reaching optimal performance at 25 nm.This phenomenon is attributed to the lateral anisotropy gradient of the Co layer,which is induced by the wedge-shaped HfO_(2)buffer layer.The thickness gradient of HfO_(2)along the wedge creates a corresponding lateral anisotropy gradient in the Co layer,correlating with the switching ratio.These findings indicate that field-free SOT switching can be achieved through designing buffer layer,offering a novel approach to innovating spin-orbit device.
基金the National Key Research and Development Program of China(Grant Nos.2022YFA1405100,2022YFA1403601,2020AAA0109005,and 2023YFB4502100)the“Pioneer”and“Leading Goose”R&D Program of Zhejiang Province(Grant No.2022C01053)+1 种基金the National Natural Science Foundation of China(Grant Nos.12174405,12204497,12327806,and 62074063)Shenzhen Science and Technology Program(Grant No.JCYJ20220818103410022).
文摘Topological magnetism with strong robustness,nanoscale dimensions and ultralow driving current density(106 A/m^(2))is promising for applications in information sensing,storage,and processing,and thus sparking widespread research interest.Exploring candidate material systems with nanoscale size and easily tunable properties is a key for realizing practical topological magnetism-based spintronic devices.Here,we propose a class of ultrathin heterostructures,Fe/Bi_(2)O_(2)X(X=S,Se,Te)by deposing metal Fe on quasi-two-dimensional(2D)bismuth oxychalcogenides Bi_(2)O_(2)X(X=S,Se,Te)with excellent ferroelectric/ferroelastic properties.Large Dzyaloshinskii–Moriya interaction(DMI)and topological magnetism can be realized.Our atomistic spin dynamics simulations demonstrate that field-free vortex–antivortex loops and sub-10 nm skyrmions exist in Fe/Bi_(2)O_(2)S and Fe/Bi_(2)O_(2)Se interfaces,respectively.These results provide a possible strategy to tailor topological magnetism in ultrathin magnets/2D materials interfaces,which is extremely vital for spintronics applications.
基金supported by the Program of Excellent Team in Harbin Institute of Technologythe Program for New Century Excellent Talents in University (NCET)National Natural Science Foundation of China (Grant Nos 10774033,60878018 and 10674036)
文摘This paper studies the molecular rotational excitation and field-free spatial alignment in a nonresonant intense laser field numerically and analytically by using the time-dependent SchrSdinger equation. The broad rotational wave packets excited by the femtosecond pulse are defined in conjugate angle space, and their coefficients are obtained by solving a set of coupled linear equations. Both single molecule orientation angles and an ensemble of O2 and CO molecule angular distributions are calculated in detail. The numerical results show that, for single molecule highest occupied molecular orbital （HOMO） symmetry σ tends to have a molecular orientation along the laser polarization direction and the permanent dipole moment diminishes the mean of the orientation angles; for an ensemble of molecules, angular distributions provide more complex and additional information at times where there are no revivals in the single molecule plot. In particular, at the revival peak instant, with the increase of temperature of the molecular ensemble, the anisotropic angular distributions with respect to the laser polarization direction of the πg orbital gradually transform to the symmetrical distributions regarding the laser polarization vector and for two HOMO configurations angular distributions of all directions are confined within a smaller angle when the temperature of the molecular ensemble is higher.
基金Project supported by the National Natural Science Foundation of China (Grants Nos. 10634020,11074014 and 10821062)
文摘Through theoretical analysis,we show how aligning pulse durations affect the degree and the time-rate slope of nitrogen field-free alignment at a fixed pulse intensity.It is found that both the degree and the slope first increase,then saturate,and finally decrease with the increasing pump duration.The optimal durations for the maximum degree and the maximum slope of the alignment are found to be different.Additionally,they are found to mainly depend on the molecular rotational period,and are affected by the temperature and the aligning pump intensities.The mechanism of molecular alignment is also discussed.
基金Project supported by the‘Pioneer’and‘Leading Goose’Research and Development Program of Zhejiang Province,China(Grant No.2022C01053)the National Natural Science Foundation of China(Grant Nos.11874135,12104119+2 种基金12004090)Key Research and Development Program of Zhejiang Province,China(Grant No.2021C01039)Natural Science Foundation of Zhejiang Province,China(Grant Nos.LQ20F040005 and LQ21A050001)。
文摘Current induced spin-orbit torque(SOT)switching of magnetization is a promising technology for nonvolatile spintronic memory and logic applications.In this work,we systematically investigated the effect of Ta thickness on the magnetic properties,field-free switching and SOT efficiency in a ferromagnetically coupled Co/Ta/Co Fe B trilayer with perpendicular magnetic anisotropy.We found that both the anisotropy field and coercivity increase with increasing Ta thickness from0.15 nm to 0.4 nm.With further increase of Ta thickness to 0.5 nm,two-step switching is observed,indicating that the two magnetic layers are magnetically decoupled.Measurements of pulse-current induced magnetization switching and harmonic Hall voltages show that the critical switching current density increases while the field-free switching ratio and SOT efficiency decrease with increasing Ta thickness.Both the enhanced spin memory loss and reduced interlayer exchange coupling might be responsible for theβ_(DL)decrease as the Ta spacer thickness increases.The studied structure with the incorporation of a Co Fe B layer is able to realize field-free switching in the strong ferromagnetic coupling region,which may contribute to the further development of magnetic tunnel junctions for better memory applications.
基金This work was supported by the“Pioneer”and“Leading Goose”RD Program of Zhejiang Province(Grant No.2022C01053)the National Natural Science Foundation of China(Grant No.12274108,11874135 and 12104119)+1 种基金the Key Research and Development Program of Zhejiang Province(Grant No.2021C01039)the Natural Science Foundation of Zhejiang Province,China(Grant Nos.LQ20F040005 and LQ21A050001).
文摘L1_(0)-FePt distinguishes itself for its ultrahigh perpendicular magnetic anisotropy(PMA),enabling thermally stabile memory cells to scale down to 3 nm.The recently discovered“bulk”spin−orbit torques in L1_(0)-FePt provide an efficient and scalable way to manipulate the L1_(0)-FePt magnetization.However,the existence of an external field during the switching limits its practical application,and therefore field-free switching of L1_(0)-FePt is highly demanded.In this manuscript,by growing the L1_(0)-FePt film on vicinal MgO(001)substrates,we realize the field-free switching of L1_(0)-FePt.This method is different from previously established strategies as it does not need to add other functional layers or create asymmetry in the film structure.The dependence on the vicinal angle,film thickness,and growth temperature demonstrates a wide operation window for the fieldfree switching of L1_(0)-FePt.We confirm the physical origin of the field-free switching is due to the tilted anisotropy of L1_(0)-FePt induced by the vicinal surface.We also quantitatively characterize the spin-orbit torques in the L1_(0)-FePt films.Our results extend beyond the established strategies to realize field-free switching,and potentially could be applied to mass production.
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.
基金supported in part by the Youth Innovation Promotion Association of Chinese Academy of Sciences(CAS)under Grant 2020118Beijing Nova Program under Grant 20230484358Beijing Superstring Academy of Memory Technology:under Grant No.E2DF06X003。
文摘Magnetoresistive random access memory(MRAM)is a promising non-volatile memory technology that can be utilized as an energy and space-efficient storage and computing solution,particularly in cache functions within circuits.Although MRAM has achieved mass production,its manufacturing process still remains challenging,resulting in only a few semiconductor companies dominating its production.In this review,we delve into the materials,processes,and devices used in MRAM,focusing on both the widely adopted spin transfer torque MRAM and the next-generation spin-orbit torque MRAM.We provide an overview of their operational mechanisms and manufacturing technologies.Furthermore,we outline the major hurdles faced in MRAM manufacturing and propose potential solutions in detail.Then,the applications of MRAM in artificial intelligent hardware are introduced.Finally,we present an outlook on the future development and applications of MRAM.
文摘为探究脱病毒种苗对果蔗的影响,本研究以广东黄皮果蔗为试验材料,进行了自留种、脱毒一代、脱毒二代果蔗种苗的田间性状和果汁品质的比较研究。结果表明,3种材料中,脱毒二代果蔗的田间生长状态最佳,与自留种和脱毒一代相比,其地上株高分别提高9.08%、5.80%(其中可食部分高度分别提高13.64%、7.19%),茎粗分别提高13.98%、9.71%,产量分别提高47.76%、63.72%(达到159.5 t hm^(-2)),出汁率分别提高3.64%、9.17%,蔗汁的总糖含量分别下降10.14%、12.73%;脱毒对果蔗蔗汁的密度、锤度和纤维含量无显著影响;脱毒苗第一代果蔗与自留种的产量和蔗汁品质无显著差异,脱毒组培苗作为第一代种苗可用于繁育脱毒果蔗种茎,3—4月份适宜移栽。因此,相对于一代组培苗,采用脱毒第二代种苗(脱毒第一代种苗种植收获的果蔗种茎)进行商品蔗种植效果更好,可促进果蔗田间生长,显著提高果蔗的产量。
