We review our recent works on dynamics of magnetization in ferromagnet with spin-transfer torque. Driven by constant spin-polarized current, the spin-transfer torque counteracts both the precession driven by the effec...We review our recent works on dynamics of magnetization in ferromagnet with spin-transfer torque. Driven by constant spin-polarized current, the spin-transfer torque counteracts both the precession driven by the effective field and the Gilbert damping term different from the common understanding. When the spin current exceeds the critical value, the conjunctive action of Gilbert damping and spin-transfer torque leads naturally the novel screw-pitch effect characterized by the temporal oscillation of domain wall velocity and width. Driven by space- and time-dependent spin-polarized current and magnetic field, we expatiate the formation of domain wall velocity in ferromagnetic nanowire. We discuss the properties of dynamic magnetic soliton in uniaxial anisotropic ferromagnetic nanowire driven by spin-transfer torque, and analyze the modulation instability and dark soliton on the spin wave background, which shows the characteristic breather behavior of the soliton as it propagates along the ferromagnetic nanowire. With stronger breather character, we get the novel magnetic rogue wave and clarify its formation mechanism. The generation of magnetic rogue wave mainly arises from the accumulation of energy and magnons toward to its central part. We also observe that the spin-polarized current can control the exchange rate of magnons between the envelope soliton and the background, and the critical current condition is obtained analytically. At last, we have theoretically investigated the current-excited and frequency-adjusted ferromagnetic resonance in magnetic trilayers. A particular case of the perpendicular analyzer reveals that the ferromagnetic resonance curves, including the resonant location and the resonant linewidth, can be adjusted by changing the pinned magnetization direction and the direct current. Under the control of the current and external magnetic field, several magnetic states, such as quasi-parallel and quasi-antiparallel stable states, out-of-plane precession, and bistable states can be realized. The precession frequency can be expressed as a function of the current and external magnetic field.展开更多
A polyvinylidene-fluoride（PVDF）-based magnetoelectric torque（MET） device is designed with elastic layer sandwiched by PVDF layers, and low-frequency MET effect is carefully studied. It is found that elastic modulu...A polyvinylidene-fluoride（PVDF）-based magnetoelectric torque（MET） device is designed with elastic layer sandwiched by PVDF layers, and low-frequency MET effect is carefully studied. It is found that elastic modulus and thickness of the elastic layer have great influences on magnetoelectric（ME） voltage coefficient（α（ME）） and working range of frequency in PVDF-based MET device. The decrease of the modulus and thickness can help increase the α ME. However,it can also reduce the working range in the low frequency. By optimizing the parameters, the giant α（ME） of 320 V/cm·Oe（1 Oe = 79.5775 A·m^-1 at low frequency（1 Hz） can be obtained. The present results may help design PVDF-based MET low-frequency magnetic sensor with improved magnetic sensitivity in a relative large frequency range.展开更多
Strong-field terahertz(THz) radiation holds significant potential in non-equilibrium state manipulation, electron acceleration, and biomedical effects. However, distortion-free detection of strong-field THz waveforms ...Strong-field terahertz(THz) radiation holds significant potential in non-equilibrium state manipulation, electron acceleration, and biomedical effects. However, distortion-free detection of strong-field THz waveforms remains an essential challenge in THz science and technology. To address this issue, we propose a ferromagnetic detection scheme based on Zeeman torque sampling, achieving distortion-free strong-field THz waveform detection in Py films. Thickness-dependent characterization(3–21 nm) identifies peak detection performance at 21 nm within the investigated range. Furthermore, by structurally engineering the Py ferromagnetic layer, we demonstrate strong-field THz detection in symmetric Ta(3 nm)/Py(9 nm)/Ta(3 nm) heterostructure while simultaneously resolving Zeeman torque responses and collective spin-wave dynamics in asymmetric W(4 nm)/Py(9 nm)/Pt(2 nm)heterostructure. We calculated spin wave excitations and spin orbit torque distributions in asymmetric heterostructures, along with spin wave excitations in symmetric modes. This approach overcomes the sensitivity limitations of conventional techniques in strong-field conditions.展开更多
The development of magnetic heterostructures with strong perpendicular magnetic anisotropy(PMA),strong spin-orbit torques(SOTs),low impedance,and good integration compatibility at the same time is central for high-per...The development of magnetic heterostructures with strong perpendicular magnetic anisotropy(PMA),strong spin-orbit torques(SOTs),low impedance,and good integration compatibility at the same time is central for high-performance spintronic memory and computing applications.Here,we report the development of the PMA superlattice[Pt/Co/W]_(n)that can be sputtered-deposited on commercial oxidized silicon substrates and has giant SOTs,strong uniaxial PMA of≈9.2 Merg/cm^(3),and rigid macrospin performance.The damping-like and field-like SOTs of the[Pt/Co/W]_(n)superlattices exhibit a linear increase with the repeat number n and reach the giant values of 225%and-33%(two orders of magnitude greater than that in clean-limit Pt)at n=12,respectively.The damping-like SOT is also of the opposite sign and much greater in magnitude than the field-like SOT,regardless of the number n.These results clarify that the spin current that generates SOTs in the[Pt/Co/W]_(n)superlattices arises predominantly from the spin Hall effect rather than bulk Rashba spin splitting,providing a unified understanding of the SOTs in these superlattices.We also demonstrate deterministic switching in thickerthan-50-nm PMA[Pt/Co/W]_(12)superlattices at a low current density.This work establishes the[Pt/Co/W]_(n)superlattice as a compelling material candidate for ultra-fast,low-power,long-retention nonvolatile spintronic memory and computing technologies.展开更多
We present an overview in the understanding of spin-transfer torque(STT) induced magnetization dynamics in spintorque nano-oscillator(STNO) devices. The STNO contains an in-plane(IP) magnetized free layer and an out-o...We present an overview in the understanding of spin-transfer torque(STT) induced magnetization dynamics in spintorque nano-oscillator(STNO) devices. The STNO contains an in-plane(IP) magnetized free layer and an out-of-plane(OP) magnetized spin polarizing layer. After a brief introduction, we first use mesoscopic micromagnetic simulations,which are based on the Landau–Lifshitz–Gilbert equation including the STT effect, to specify how a spin-torque term may tune the magnetization precession orbits of the free layer, showing that the oscillator frequency is proportional to the current density and the z-component of the free layer magnetization. Next, we propose a pendulum-like model within the macrospin approximation to describe the dynamic properties in such type of STNOs. After that, we further show the procession dynamics of the STNOs excited by IP and OP dual spin-polarizers. Both the numerical simulations and analytical theory indicate that the precession frequency is linearly proportional to the spin-torque of the OP polarizer only and is irrelevant to the spin-torque of the IP polarizer. Finally, a promising approach of coordinate transformation from the laboratory frame to the rotation frame is introduced, by which the nonstationary OP magnetization precession process is therefore transformed into the stationary process in the rotation frame. Through this method, a promising digital frequency shift-key modulation technique is presented, in which the magnetization precession can be well controlled at a given orbit as well as its precession frequency can be tuned with the co-action of spin polarized current and magnetic field(or electric field) pulses.展开更多
Spintronics is a new discipline focusing on the research and application of electronic spin properties. After the discovery of the giant magnetoresistance effect in 1988, spintronics has had a huge impact on scientifi...Spintronics is a new discipline focusing on the research and application of electronic spin properties. After the discovery of the giant magnetoresistance effect in 1988, spintronics has had a huge impact on scientific progress and related applications in the development of information technology. In recent decades, the main motivation in spintronics has been efficiently controlling local magnetization using electron flow or voltage rather than controlling the electron flow using magnetization. Using spin-orbit coupling in a material can convert a charge current into a pure spin current(a flow of spin momenta without a charge flow) and generate a spin-orbit torque on the adjacent ferromagnets. The ability of spintronic devices to utilize spin-orbit torques to manipulate the magnetization has resulted in large-scale developments such as magnetic random-access memories and has boosted the spintronic research area. Here in, we review the theoretical and experimental results that have established this subfield of spintronics. We introduce the concept of a pure spin current and spin-orbit torques within the experimental framework, and we review transport-, magnetization-dynamics-, and opticalbased measurements and link then to both phenomenological and microscopic theories of the effect. The focus is on the related progress reported from Chinese universities and institutes, and we specifically highlight the contributions made by Chinese researchers.展开更多
The current-induced spin-orbit torque(SOT)plays a dominant role to manipulate the magnetization in a heavy metal/ferromagnetic metal bilayer.We separate the contributions of interfacial and bulk spin-orbit coupling(SO...The current-induced spin-orbit torque(SOT)plays a dominant role to manipulate the magnetization in a heavy metal/ferromagnetic metal bilayer.We separate the contributions of interfacial and bulk spin-orbit coupling(SOC)to the effective field of field-like SOT in a typical NiFe/Pt bilayer by planar Hall effect(PHE).The effective field from interfacial SOC is directly measured at the transverse PHE configuration.Then,at the longitudinal configuration,the effective field from bulk SOC is determined,which is much smaller than that from interfacial SOC.The giant interface SOT in NiFe/Pt bilayers suggests that further analysis of interfacial effects on the current-induced manipulation of magnetization is necessary.展开更多
We study inserting Co layer thickness-dependent spin transport and spin-orbit torques(SOTs)in the Pt/Co/Py trilayers by spin-torque ferromagnetic resonance.The interfacial perpendicular magnetic anisotropy(IPMA)energy...We study inserting Co layer thickness-dependent spin transport and spin-orbit torques(SOTs)in the Pt/Co/Py trilayers by spin-torque ferromagnetic resonance.The interfacial perpendicular magnetic anisotropy(IPMA)energy density(Ks=2.7 erg/cm^(2),1 erg=10^(-7) J),which is dominated by interfacial spin-orbit coupling(ISOC)in the Pt/Co interface,total effective spin-mixing conductance(G↑↓eff,tot=0.42×10^(15) Ω^(-1)·m^(-2))and two-magnon scattering(βTMS=0.46 nm2)are first characterized,and the damping-like torque(ξDL=0.103)and field-like torque(ξFL=-0.017)efficiencies are also calculated quantitatively by varying the thickness of the inserting Co layer.The significant enhancement of ξDL and ξFL in Pt/Co/Py than Pt/Py bilayer system originates from the interfacial Rashba-Edelstein effect due to the strong ISOC between Co-3d and Pt-5d orbitals at the Pt/Co interface.Additionally,we find a considerable out-of-plane spin polarization SOT,which is ascribed to the spin anomalous Hall effect and possible spin precession effect due to IPMA-induced perpendicular magnetization at the Pt/Co interface.Our results demonstrate that the ISOC of the Pt/Co interface plays a vital role in spin transport and SOTs-generation.Our finds offer an alternative approach to improve the conventional SOTs efficiencies and generate unconventional SOTs with out-of-plane spin polarization to develop low power Pt-based spintronic via tailoring the Pt/FM interface.展开更多
Twisted polymer artificial muscles activated by thermal heating represent a new class of soft actuators capable of generating torsional actuation.The thermal torsion effect,characterized by the reversible untwisting o...Twisted polymer artificial muscles activated by thermal heating represent a new class of soft actuators capable of generating torsional actuation.The thermal torsion effect,characterized by the reversible untwisting of twisted fibers as temperature increases due to greater radial than axial thermal expansion,is crucial to the actuation performance of these artificial muscles.This study explores the thermal torsion effect of polymer muscles made of twisted Nylon 6 fibers in experimental and theoretical aspects,focusing on the interplay between material properties and temperature.It is revealed that the thermal torsion effect enhances the actuation performance of the twisted polymer actuator while the thermal softening effect diminishes it.A thermal-mechanical model incorporating both the thermal torsion effect and thermal softening effect is used to predict the recovered torque of the twisted polymer actuators.An optimal bias angle and operating temperature are identified to maximize the recovered torque.Analysis of strain and stress distributions in the cross-section of the twisted polymer fiber shows that the outer layers of the fiber predominantly contribute to the torsional actuation.This work aids in the precise control and structural optimization of the thermally-activated twisted polymer actuators.展开更多
We investigate a continuous Heisenberg spin chain equation which models the local magnetization in ferromagnet with time-and site-dependent inhomogeneous bilinear interaction and timedependent spin-transfer torque.By ...We investigate a continuous Heisenberg spin chain equation which models the local magnetization in ferromagnet with time-and site-dependent inhomogeneous bilinear interaction and timedependent spin-transfer torque.By establishing the gauge equivalence between the spin chain equation and an integrable generalized nonlinear Schrödinger equation,we present explicitly a novel nonautonomous magnetic soliton solution for the spin chain equation.The results display how the dynamics of the magnetic soliton can be controlled by the bilinear interaction and spin-polarized current.Especially,we find that the site-dependent bilinear interaction may break some conserved quantity,and give rise to damping-like effect in the spin evolution.展开更多
Magnetization orientation of a nanoscale ferromagnet can be manipulated by an electric current via spin-transfer torque(STT) effect,which holds great promise in the applications of non-volatile magnetic random access ...Magnetization orientation of a nanoscale ferromagnet can be manipulated by an electric current via spin-transfer torque(STT) effect,which holds great promise in the applications of non-volatile magnetic random access memory(MRAM) and spintorque oscillators.We review the fundamental mechanism and experimental progress of the STT effect.Then,different formula of STT torque has been classified,which can be added to the conventional Landau-Lifshitz-Gilbert equation.After that,we show some simulation results that mainly concern the STT-driven vortex dynamics,magnetization oscillations excited by a perpendicular polarizer,and the detail dynamics by in-plane and out-of-plane dual spin polarizers.展开更多
Although InterTAN(IT)nails are widely employed to treat femoral intertrochanteric fractures,the mechanism behind the tautening effect of titanium-alloy IT nails is not well understood.This study aimed to reveal the me...Although InterTAN(IT)nails are widely employed to treat femoral intertrochanteric fractures,the mechanism behind the tautening effect of titanium-alloy IT nails is not well understood.This study aimed to reveal the mechanism of this effect.A torque test experiment was conducted,with the torque value recorded and transformed to obtain the tautening effect.Then,theoretical and finite element analyses were performed to further understand the mechanism.The influence of age and pitch-difference on the tautening effect was also examined in the study,the results attributed to the pitch-varying integrated interlocking lag screw.The torque and the corresponding tautening effect drastically increase as the screw is inserted deeper during the second stage,while the torque measured in the first stage is always zero.Additionally,the tautening force increases with increasing age,this relationship helps evaluate the effect at different ages.The tautening effect also increases nearly linearly with the pitch difference,which can be adjusted during the IT design stage to select or design IT in engineering practice.展开更多
We report the development of the[Pt_(0.75)Ti_(0.25)/Co-Ni multilayer/Ta]_n superlattice with strong spin-orbit torque,large perpendicular magnetic anisotropy,and remarkably low switching current density.We demonstrate...We report the development of the[Pt_(0.75)Ti_(0.25)/Co-Ni multilayer/Ta]_n superlattice with strong spin-orbit torque,large perpendicular magnetic anisotropy,and remarkably low switching current density.We demonstrate that the efficiency of the spin-orbit torque increases nearly linearly with the repetition number n,which is in excellent agreement with the spin Hall effect of the Pt_(0.75)Ti_(0.25)being essentially the only source of the observed spin-orbit torque.The perpendicular magnetic anisotropy field is also substantially enhanced by more than a factor of 2 as n increases from 1 to6.The[Pt_(0.75)Ti_(0.25)/Co-Ni multilayers/Ta]_n superlattice additionally exhibits deterministic,low-current-density magnetization switching despite the very large total layer thicknesses.The unique combination of strong spin-orbit torque,robust perpendicular magnetic anisotropy,low-current-density switching,and excellent high thermal stability makes the[Pt_(0.75)Ti_(0.25)/Co-Ni multilayer/Ta]_n superlattice a highly compelling material candidate for ultrafast,energy-efficient,and long-data-retention spintronic technologies.展开更多
Humanoid robot joints require real-time torque detection to provide accurate force feedback informa-tion for the control system.To meet the measurement requirements and realize the miniaturization of the sensor,a torq...Humanoid robot joints require real-time torque detection to provide accurate force feedback informa-tion for the control system.To meet the measurement requirements and realize the miniaturization of the sensor,a torque sensor based on the magnetoelastic effect is developed,utilizing planar spiral coils as detection probes.In this work,a planar spiral coil mutual inductance calculation model is established to solve the mutual inductance coefficient,and the mechanical structure and circuit design of the sensor are completed.Finally,a torque loading platform is built to perform calibration experiments,and the hysteresis model is improved to compensate for the hysteresis phenomenon.The calibration results indicate that the sensor shows excellent loaded nonlinearity of 3.08%F.S.,unloaded nonlinearity of 2.71% F.S.,loaded repeatability of 2.48% F.S.,unloaded repeatability of 1.89% F.S.and hysteresis of 1.9% F.S.,at a compact probe size of 13.8×9.9×1.8 mm.展开更多
基金supported by the Natural Science Foundation of Hebei Province of China(Grant No.A2012202022)supported by the Aid Program for Young Teachers of Hunan University,the Project-sponsored by SRF for ROCS,SEM+2 种基金the Aid Program for Science and Technology Innovative Research Team in Higher Educational Institution of Hunan Province,Chinasupported by the National Basic Research Program of China(Grant Nos.2011CB921502 and 2012CB821305)the National Natural Science Foundation of China(Grant Nos.61227902 and 61378017)
文摘We review our recent works on dynamics of magnetization in ferromagnet with spin-transfer torque. Driven by constant spin-polarized current, the spin-transfer torque counteracts both the precession driven by the effective field and the Gilbert damping term different from the common understanding. When the spin current exceeds the critical value, the conjunctive action of Gilbert damping and spin-transfer torque leads naturally the novel screw-pitch effect characterized by the temporal oscillation of domain wall velocity and width. Driven by space- and time-dependent spin-polarized current and magnetic field, we expatiate the formation of domain wall velocity in ferromagnetic nanowire. We discuss the properties of dynamic magnetic soliton in uniaxial anisotropic ferromagnetic nanowire driven by spin-transfer torque, and analyze the modulation instability and dark soliton on the spin wave background, which shows the characteristic breather behavior of the soliton as it propagates along the ferromagnetic nanowire. With stronger breather character, we get the novel magnetic rogue wave and clarify its formation mechanism. The generation of magnetic rogue wave mainly arises from the accumulation of energy and magnons toward to its central part. We also observe that the spin-polarized current can control the exchange rate of magnons between the envelope soliton and the background, and the critical current condition is obtained analytically. At last, we have theoretically investigated the current-excited and frequency-adjusted ferromagnetic resonance in magnetic trilayers. A particular case of the perpendicular analyzer reveals that the ferromagnetic resonance curves, including the resonant location and the resonant linewidth, can be adjusted by changing the pinned magnetization direction and the direct current. Under the control of the current and external magnetic field, several magnetic states, such as quasi-parallel and quasi-antiparallel stable states, out-of-plane precession, and bistable states can be realized. The precession frequency can be expressed as a function of the current and external magnetic field.
基金supported by the National Natural Science Foundation of China(Grant Nos.51525103,51522105,and 11304326)the National Key Technology Research and Development Program of China(Grant No.2016YFA0201102)+1 种基金Ningbo Municipal Science and Technology Innovation Team,China(Grant No.2015B11001)the Ningbo Municipal Major Science and Technology Projects,China(Grant No.2015B11027)
文摘A polyvinylidene-fluoride（PVDF）-based magnetoelectric torque（MET） device is designed with elastic layer sandwiched by PVDF layers, and low-frequency MET effect is carefully studied. It is found that elastic modulus and thickness of the elastic layer have great influences on magnetoelectric（ME） voltage coefficient（α（ME）） and working range of frequency in PVDF-based MET device. The decrease of the modulus and thickness can help increase the α ME. However,it can also reduce the working range in the low frequency. By optimizing the parameters, the giant α（ME） of 320 V/cm·Oe（1 Oe = 79.5775 A·m^-1 at low frequency（1 Hz） can be obtained. The present results may help design PVDF-based MET low-frequency magnetic sensor with improved magnetic sensitivity in a relative large frequency range.
基金supported by the Scientific Research Innovation Capability Support Project for Young Faculty (Grant No.ZYGXQNJSKYCXNLZCXMI3)the National Key Research and Development Program of China (Grant No.2022YFA1604402)+1 种基金the National Natural Science Foundation of China (Grant Nos.U23A6002,92250307,and 52225106)the Beijing Municipal Science and Technology Commission,Administrative Commission of Zhongguancun Science Park (Grant No.Z25110000692500)。
文摘Strong-field terahertz(THz) radiation holds significant potential in non-equilibrium state manipulation, electron acceleration, and biomedical effects. However, distortion-free detection of strong-field THz waveforms remains an essential challenge in THz science and technology. To address this issue, we propose a ferromagnetic detection scheme based on Zeeman torque sampling, achieving distortion-free strong-field THz waveform detection in Py films. Thickness-dependent characterization(3–21 nm) identifies peak detection performance at 21 nm within the investigated range. Furthermore, by structurally engineering the Py ferromagnetic layer, we demonstrate strong-field THz detection in symmetric Ta(3 nm)/Py(9 nm)/Ta(3 nm) heterostructure while simultaneously resolving Zeeman torque responses and collective spin-wave dynamics in asymmetric W(4 nm)/Py(9 nm)/Pt(2 nm)heterostructure. We calculated spin wave excitations and spin orbit torque distributions in asymmetric heterostructures, along with spin wave excitations in symmetric modes. This approach overcomes the sensitivity limitations of conventional techniques in strong-field conditions.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFA1204000)the Beijing National Natural Science Foundation(Grant No.Z230006)the National Natural Science Foundation of China(Grant Nos.12304155 and 12274405).
文摘The development of magnetic heterostructures with strong perpendicular magnetic anisotropy(PMA),strong spin-orbit torques(SOTs),low impedance,and good integration compatibility at the same time is central for high-performance spintronic memory and computing applications.Here,we report the development of the PMA superlattice[Pt/Co/W]_(n)that can be sputtered-deposited on commercial oxidized silicon substrates and has giant SOTs,strong uniaxial PMA of≈9.2 Merg/cm^(3),and rigid macrospin performance.The damping-like and field-like SOTs of the[Pt/Co/W]_(n)superlattices exhibit a linear increase with the repeat number n and reach the giant values of 225%and-33%(two orders of magnitude greater than that in clean-limit Pt)at n=12,respectively.The damping-like SOT is also of the opposite sign and much greater in magnitude than the field-like SOT,regardless of the number n.These results clarify that the spin current that generates SOTs in the[Pt/Co/W]_(n)superlattices arises predominantly from the spin Hall effect rather than bulk Rashba spin splitting,providing a unified understanding of the SOTs in these superlattices.We also demonstrate deterministic switching in thickerthan-50-nm PMA[Pt/Co/W]_(12)superlattices at a low current density.This work establishes the[Pt/Co/W]_(n)superlattice as a compelling material candidate for ultra-fast,low-power,long-retention nonvolatile spintronic memory and computing technologies.
基金supported by the National Basic Research Program of China(Grant No.2015CB921501)the National Natural Science Foundation of China(Grant Nos.11774260,51671057,and 11874120)
文摘We present an overview in the understanding of spin-transfer torque(STT) induced magnetization dynamics in spintorque nano-oscillator(STNO) devices. The STNO contains an in-plane(IP) magnetized free layer and an out-of-plane(OP) magnetized spin polarizing layer. After a brief introduction, we first use mesoscopic micromagnetic simulations,which are based on the Landau–Lifshitz–Gilbert equation including the STT effect, to specify how a spin-torque term may tune the magnetization precession orbits of the free layer, showing that the oscillator frequency is proportional to the current density and the z-component of the free layer magnetization. Next, we propose a pendulum-like model within the macrospin approximation to describe the dynamic properties in such type of STNOs. After that, we further show the procession dynamics of the STNOs excited by IP and OP dual spin-polarizers. Both the numerical simulations and analytical theory indicate that the precession frequency is linearly proportional to the spin-torque of the OP polarizer only and is irrelevant to the spin-torque of the IP polarizer. Finally, a promising approach of coordinate transformation from the laboratory frame to the rotation frame is introduced, by which the nonstationary OP magnetization precession process is therefore transformed into the stationary process in the rotation frame. Through this method, a promising digital frequency shift-key modulation technique is presented, in which the magnetization precession can be well controlled at a given orbit as well as its precession frequency can be tuned with the co-action of spin polarized current and magnetic field(or electric field) pulses.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674142,51771099,11429401,and 51471081)the Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT-16R35)
文摘Spintronics is a new discipline focusing on the research and application of electronic spin properties. After the discovery of the giant magnetoresistance effect in 1988, spintronics has had a huge impact on scientific progress and related applications in the development of information technology. In recent decades, the main motivation in spintronics has been efficiently controlling local magnetization using electron flow or voltage rather than controlling the electron flow using magnetization. Using spin-orbit coupling in a material can convert a charge current into a pure spin current(a flow of spin momenta without a charge flow) and generate a spin-orbit torque on the adjacent ferromagnets. The ability of spintronic devices to utilize spin-orbit torques to manipulate the magnetization has resulted in large-scale developments such as magnetic random-access memories and has boosted the spintronic research area. Here in, we review the theoretical and experimental results that have established this subfield of spintronics. We introduce the concept of a pure spin current and spin-orbit torques within the experimental framework, and we review transport-, magnetization-dynamics-, and opticalbased measurements and link then to both phenomenological and microscopic theories of the effect. The focus is on the related progress reported from Chinese universities and institutes, and we specifically highlight the contributions made by Chinese researchers.
基金the National Natural Science Foundation of China(Grant No.11574375).
文摘The current-induced spin-orbit torque(SOT)plays a dominant role to manipulate the magnetization in a heavy metal/ferromagnetic metal bilayer.We separate the contributions of interfacial and bulk spin-orbit coupling(SOC)to the effective field of field-like SOT in a typical NiFe/Pt bilayer by planar Hall effect(PHE).The effective field from interfacial SOC is directly measured at the transverse PHE configuration.Then,at the longitudinal configuration,the effective field from bulk SOC is determined,which is much smaller than that from interfacial SOC.The giant interface SOT in NiFe/Pt bilayers suggests that further analysis of interfacial effects on the current-induced manipulation of magnetization is necessary.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11774150,12074178,11874135,and 12004171)the Applied Basic Research Programs of the Science and Technology Commission Foundation of Jiangsu Province,China(Grant No.BK20200309)+1 种基金the Open Research Fund of Jiangsu Provincial Key Laboratory for Nanotechnology,Key Research and Development Program of Zhejiang Province,China(Grant No.2021C01039)the Scientific Foundation of Nanjing University of Posts and Telecommunications(Grant No.NY220164).
文摘We study inserting Co layer thickness-dependent spin transport and spin-orbit torques(SOTs)in the Pt/Co/Py trilayers by spin-torque ferromagnetic resonance.The interfacial perpendicular magnetic anisotropy(IPMA)energy density(Ks=2.7 erg/cm^(2),1 erg=10^(-7) J),which is dominated by interfacial spin-orbit coupling(ISOC)in the Pt/Co interface,total effective spin-mixing conductance(G↑↓eff,tot=0.42×10^(15) Ω^(-1)·m^(-2))and two-magnon scattering(βTMS=0.46 nm2)are first characterized,and the damping-like torque(ξDL=0.103)and field-like torque(ξFL=-0.017)efficiencies are also calculated quantitatively by varying the thickness of the inserting Co layer.The significant enhancement of ξDL and ξFL in Pt/Co/Py than Pt/Py bilayer system originates from the interfacial Rashba-Edelstein effect due to the strong ISOC between Co-3d and Pt-5d orbitals at the Pt/Co interface.Additionally,we find a considerable out-of-plane spin polarization SOT,which is ascribed to the spin anomalous Hall effect and possible spin precession effect due to IPMA-induced perpendicular magnetization at the Pt/Co interface.Our results demonstrate that the ISOC of the Pt/Co interface plays a vital role in spin transport and SOTs-generation.Our finds offer an alternative approach to improve the conventional SOTs efficiencies and generate unconventional SOTs with out-of-plane spin polarization to develop low power Pt-based spintronic via tailoring the Pt/FM interface.
基金support from the National Natural Science Foundation of China(Grant No.12272146)the Fundamental Research Funds for the Central Universities(Grant No.2024BRA009)the Young Top-notch Talent Cultivation Program of Hubei Province,is appreciated.
文摘Twisted polymer artificial muscles activated by thermal heating represent a new class of soft actuators capable of generating torsional actuation.The thermal torsion effect,characterized by the reversible untwisting of twisted fibers as temperature increases due to greater radial than axial thermal expansion,is crucial to the actuation performance of these artificial muscles.This study explores the thermal torsion effect of polymer muscles made of twisted Nylon 6 fibers in experimental and theoretical aspects,focusing on the interplay between material properties and temperature.It is revealed that the thermal torsion effect enhances the actuation performance of the twisted polymer actuator while the thermal softening effect diminishes it.A thermal-mechanical model incorporating both the thermal torsion effect and thermal softening effect is used to predict the recovered torque of the twisted polymer actuators.An optimal bias angle and operating temperature are identified to maximize the recovered torque.Analysis of strain and stress distributions in the cross-section of the twisted polymer fiber shows that the outer layers of the fiber predominantly contribute to the torsional actuation.This work aids in the precise control and structural optimization of the thermally-activated twisted polymer actuators.
文摘We investigate a continuous Heisenberg spin chain equation which models the local magnetization in ferromagnet with time-and site-dependent inhomogeneous bilinear interaction and timedependent spin-transfer torque.By establishing the gauge equivalence between the spin chain equation and an integrable generalized nonlinear Schrödinger equation,we present explicitly a novel nonautonomous magnetic soliton solution for the spin chain equation.The results display how the dynamics of the magnetic soliton can be controlled by the bilinear interaction and spin-polarized current.Especially,we find that the site-dependent bilinear interaction may break some conserved quantity,and give rise to damping-like effect in the spin evolution.
基金support by the National Natural Science Foundation of China(Grant Nos.11074046,11274241,51171047 and 51222103)the Shuguang Program of Shanghai Education Commission(Grant No.09SG22)the New Century Educational Talents Plan of Chinese Education Ministry(Grant No.NCET-10-0603)
文摘Magnetization orientation of a nanoscale ferromagnet can be manipulated by an electric current via spin-transfer torque(STT) effect,which holds great promise in the applications of non-volatile magnetic random access memory(MRAM) and spintorque oscillators.We review the fundamental mechanism and experimental progress of the STT effect.Then,different formula of STT torque has been classified,which can be added to the conventional Landau-Lifshitz-Gilbert equation.After that,we show some simulation results that mainly concern the STT-driven vortex dynamics,magnetization oscillations excited by a perpendicular polarizer,and the detail dynamics by in-plane and out-of-plane dual spin polarizers.
基金financially supported by the International Research Cooperation Seed Fund of Beijing University of Technology (No.2021A10)Medical Industry Excellence and Innovation Program Fund of Beihang University (No.KG16180401)。
文摘Although InterTAN(IT)nails are widely employed to treat femoral intertrochanteric fractures,the mechanism behind the tautening effect of titanium-alloy IT nails is not well understood.This study aimed to reveal the mechanism of this effect.A torque test experiment was conducted,with the torque value recorded and transformed to obtain the tautening effect.Then,theoretical and finite element analyses were performed to further understand the mechanism.The influence of age and pitch-difference on the tautening effect was also examined in the study,the results attributed to the pitch-varying integrated interlocking lag screw.The torque and the corresponding tautening effect drastically increase as the screw is inserted deeper during the second stage,while the torque measured in the first stage is always zero.Additionally,the tautening force increases with increasing age,this relationship helps evaluate the effect at different ages.The tautening effect also increases nearly linearly with the pitch difference,which can be adjusted during the IT design stage to select or design IT in engineering practice.
基金supported by the Beijing Natural Science Foundation(Grant No.Z230006)the National Key Research and Development Program of China(Grant No.2022YFA1204000)the National Natural Science Foundation of China(Grant Nos.12274405 and 12393831)。
文摘We report the development of the[Pt_(0.75)Ti_(0.25)/Co-Ni multilayer/Ta]_n superlattice with strong spin-orbit torque,large perpendicular magnetic anisotropy,and remarkably low switching current density.We demonstrate that the efficiency of the spin-orbit torque increases nearly linearly with the repetition number n,which is in excellent agreement with the spin Hall effect of the Pt_(0.75)Ti_(0.25)being essentially the only source of the observed spin-orbit torque.The perpendicular magnetic anisotropy field is also substantially enhanced by more than a factor of 2 as n increases from 1 to6.The[Pt_(0.75)Ti_(0.25)/Co-Ni multilayers/Ta]_n superlattice additionally exhibits deterministic,low-current-density magnetization switching despite the very large total layer thicknesses.The unique combination of strong spin-orbit torque,robust perpendicular magnetic anisotropy,low-current-density switching,and excellent high thermal stability makes the[Pt_(0.75)Ti_(0.25)/Co-Ni multilayer/Ta]_n superlattice a highly compelling material candidate for ultrafast,energy-efficient,and long-data-retention spintronic technologies.
基金supported in part by Guangxi Science and Technology Program,China(2024AB12006)the Open Fund of Innovation Center for Control Actuators,China(ICCA18-202405)China Huaneng Group.,Ltd.Headquarters Technology Project(HNKJ24-HF15).
文摘Humanoid robot joints require real-time torque detection to provide accurate force feedback informa-tion for the control system.To meet the measurement requirements and realize the miniaturization of the sensor,a torque sensor based on the magnetoelastic effect is developed,utilizing planar spiral coils as detection probes.In this work,a planar spiral coil mutual inductance calculation model is established to solve the mutual inductance coefficient,and the mechanical structure and circuit design of the sensor are completed.Finally,a torque loading platform is built to perform calibration experiments,and the hysteresis model is improved to compensate for the hysteresis phenomenon.The calibration results indicate that the sensor shows excellent loaded nonlinearity of 3.08%F.S.,unloaded nonlinearity of 2.71% F.S.,loaded repeatability of 2.48% F.S.,unloaded repeatability of 1.89% F.S.and hysteresis of 1.9% F.S.,at a compact probe size of 13.8×9.9×1.8 mm.
