We investigate the origin of the 1/3 magnetization plateau in the S=1/2 kagome antiferromagnetic Heisenberg model using the variational Monte Carlo and exact diagonalization methods,to account for the recent experimen...We investigate the origin of the 1/3 magnetization plateau in the S=1/2 kagome antiferromagnetic Heisenberg model using the variational Monte Carlo and exact diagonalization methods,to account for the recent experimental observations in YCu_(3)(OH)_(6+x)Br_(3-x)and YCu_(3)(OD)_(6+x)Br_(3-x).We identify three degenerate valencebond-solid(VBS)states forming a√3×√3 unit cell.These states exhibit David-star patterns in the spin moment distribution with only two fractional values-1/3 and 2/3,and are related through translational transformations.While the spin correlations in these VBS states are found to be short-range,resembling a quantum spin liquid,we show that they have a vanishing topological entanglement entropy and thus are topologically trivial many-body states.Our theoretical results provide strong evidence that the 1/3 magnetization plateau observed in recent experiments arises from these√3×√3 VBS states with fractional spin moments.展开更多
就Bethuel,Brezis和Helein提出的问题讨论了Planar Ferromagnets and Antiferromagnets泛函在H={u(x)=(sinf(r)|xx|,cosf(r))∈H1(B1,S2);f(0)=0,f(1)=2π,r=|x|}中的径向极小元的一些性质,其中包括此泛函的径向极小元的零点的分布及若...就Bethuel,Brezis和Helein提出的问题讨论了Planar Ferromagnets and Antiferromagnets泛函在H={u(x)=(sinf(r)|xx|,cosf(r))∈H1(B1,S2);f(0)=0,f(1)=2π,r=|x|}中的径向极小元的一些性质,其中包括此泛函的径向极小元的零点的分布及若干个上界估计,并给出了这一问题的肯定回答.展开更多
A quantum spin liquid (QSL) is an exotic quantum ground state that does not break conventional symmetries and where the spins in the system remain dynamic down to zero temperature. Unlike a trivial paramagnetic state,...A quantum spin liquid (QSL) is an exotic quantum ground state that does not break conventional symmetries and where the spins in the system remain dynamic down to zero temperature. Unlike a trivial paramagnetic state, it features long-range quantum entanglement and supports fractionalized excitations.展开更多
Magnon-magnon coupling in synthetic antiferromagnets advances it as hybrid magnonic systems to explore the quantum information technologies.To induce magnon-magnon coupling,the parity symmetry between two magnetizatio...Magnon-magnon coupling in synthetic antiferromagnets advances it as hybrid magnonic systems to explore the quantum information technologies.To induce magnon-magnon coupling,the parity symmetry between two magnetization needs to be broken.Here we experimentally demonstrate a convenient method to break the parity symmetry by the asymmetric structure.We successfully introduce a magnon-magnon coupling in Ir-based synthetic antiferromagnets CoFeB(10 nm)/Ir(t_(Ir)=0.6 nm,1.2 nm)/CoFeB(13 nm).Remarkably,we find that the weakly uniaxial anisotropy field(-20 Oe)makes the magnon-magnon coupling anisotropic.The coupling strength presented by a characteristic anticrossing gap varies in the range between 0.54 GHz and 0.90 GHz for t_(Ir)=0.6 nm,and between 0.09 GHz and 1.4 GHz for t_(Ir)=1.2 nm.Our results demonstrate a feasible way to induce magnon-magnon coupling by an asymmetric structure and tune the coupling strength by varying the direction of in-plane magnetic field.The magnon-magnon coupling in this highly tunable material system could open exciting perspectives for exploring quantum-mechanical coupling phenomena.展开更多
Antiferromagnets offer considerable potential for electronic device applications. This article reviews recent demonstrations of spin manipulation in antiferromagnetic devices using applied electrical currents. Due to ...Antiferromagnets offer considerable potential for electronic device applications. This article reviews recent demonstrations of spin manipulation in antiferromagnetic devices using applied electrical currents. Due to spin–orbit coupling in environments with particular crystalline or structural symmetries, the electric current can induce an effective magnetic field with a sign that alternates on the lengthscale of the unit cell. The staggered effective field provides an efficient mechanism for switching antiferromagnetic domains and moving antiferromagnetic domain walls, with writing speeds in the terahertz regime.展开更多
To study the effects of lanthanide ions on the geometrically frustrated antiferromagnets and their magnetic properties,we grew high-quality single crystals of LnCu_(3)(OH)_(6)Br_(3)(Ln=Nd,Sm,and Eu)by hydrothermal met...To study the effects of lanthanide ions on the geometrically frustrated antiferromagnets and their magnetic properties,we grew high-quality single crystals of LnCu_(3)(OH)_(6)Br_(3)(Ln=Nd,Sm,and Eu)by hydrothermal method and studied their crystal structures and magnetic properties.The refinements of the crystal structure referred to the powder x-ray diffraction data show that LnCu_(3)(OH)_(6)Br_(3)adopt a Kapellasite-type layer structure,which is isostructural to their chlorine analogue.Magnetic susceptibilities demonstrate that LnCu_(3)(OH)_(6)Br_(3)have strong antiferromagnetic coupling and a pronounced magnetic frustration effect.Magnetization measurements indicate canted antiferromagnetic ordering of Cu^(2+)ions around 16 K within the kagoméplane and weak ferromagnetic coupling.Moreover,shoulder-like anomalies in specific heat around 16 K could be a signature of emergent of magnetic ordering.The low-temperature negative magnetization and specific heat of LnCu_(3)(OH)_(6)Br_(3)(Ln=Nd,Sm,and Eu)indicate that Ln^(3+)ions induce more exotic magnetic ground state properties.展开更多
Perpendicular synthetic-antiferromagnet(p-SAF) has broad applications in spin-transfer-torque magnetic random access memory and magnetic sensors. In this study, the p-SAF films consisting of (Co/Ni)3]/Ir(tIr)/[(Ni/Co)...Perpendicular synthetic-antiferromagnet(p-SAF) has broad applications in spin-transfer-torque magnetic random access memory and magnetic sensors. In this study, the p-SAF films consisting of (Co/Ni)3]/Ir(tIr)/[(Ni/Co)3are fabricated by magnetron sputtering technology. We study the domain structure and switching field distribution in p-SAF by changing the thickness of the infrared space layer. The strongest exchange coupling field(Hex) is observed when the thickness of Ir layer(tIr) is 0.7 nm and becoming weak according to the Ruderman–Kittel–Kasuya–Yosida-type coupling at 1.05 nm,2.1 nm, 4.55 nm, and 4.9 nm in sequence. Furthermore, the domain switching process between the upper Co/Ni stack and the bottom Co/Ni stack is different because of the antiferromagnet coupling. Compared with ferromagnet coupling films, the antiferromagnet samples possess three irreversible reversal regions in the first-order reversal curve distribution.With tIrincreasing, these irreversible reversal regions become denser and smaller. The results from this study will help us understand the details of the magnetization reversal process in the p-SAF.展开更多
Unconventional antiferromagnets(AFMs)with non-relativistic spin-splitting,such as the recently discovered altermagnet,have recently gained significant interest due to their potential for novel quantum phenomena and sp...Unconventional antiferromagnets(AFMs)with non-relativistic spin-splitting,such as the recently discovered altermagnet,have recently gained significant interest due to their potential for novel quantum phenomena and spintronic applications.The compensated magnetization in unconventional AFMs is protected by spin-space symmetries.In this work,we explore the symmetrybreaking effects and identify three distinct mechanisms for inducing net spin magnetizations in unconventional AFMs with collinear or non-collinear spins:(1)finite size effect,(2)extrinsic spin canting effect,and(3)irradiation with circularly polarized light.We show that the induced spin magnetizations are controllable and manifest as diverse intriguing phenomena.For the finite size system,the confined direction of a two-dimensional AM creates quantum-well-like subbands that determine the spin magnetization.This effect can be experimentally probed by measuring the spin density of states and the spin-polarization of Andreev-bound states within planar Josephson junctions.In the case of spin canting effect,it leads to peculiar anisotropic and non-monotonic behaviors in the superconducting proximity effect.Lastly,with circularly polarized light,spin magnetization is driven by the polarized light and the chirality of non-collinear magnetic order,thus offering a direct means of detecting the chirality of magnetic order in real materials.Our findings provide valuable insight into understanding and probing the spin magnetization in unconventional AFM materials.展开更多
In this paper,the global existence and uniqueness of a smooth solution to the periodic initial-value problem of the spin equations of antiferromagnets in 1 dimension are proved.
Exotic quantum spin liquid (QSL) states and fractionalized quasiparticles in frustrated magnets are of much current interest in theoretical and experimental studies of quantum magnetism. The kagome-lattice Heisenberg ...Exotic quantum spin liquid (QSL) states and fractionalized quasiparticles in frustrated magnets are of much current interest in theoretical and experimental studies of quantum magnetism. The kagome-lattice Heisenberg antiferromagnet (KAFM) provides a possible realization of just such novel topological states of matter. The kagome lattice shown in Fig. 1 is one of eleven Archimedean lattices in two spatial dimensions, where the word kagome itself means uweave pattera" in Japanese.展开更多
Ferromagnets play an important role in our daily lives,in such common devies as:compasses,electric motors and hard disks.For a long time,the antiferromagnetic(AFM)materials have been ignored for the applications.Even ...Ferromagnets play an important role in our daily lives,in such common devies as:compasses,electric motors and hard disks.For a long time,the antiferromagnetic(AFM)materials have been ignored for the applications.Even the Nobel laureate L.Néel said that antiferromagnets are interesting,but useless.展开更多
The tunneling behavior of the Néel vector out of metastable easy directions or between degenerate easy directions is studied for a small single\|domain antiferromagnetic particle at low temperature. The quantum t...The tunneling behavior of the Néel vector out of metastable easy directions or between degenerate easy directions is studied for a small single\|domain antiferromagnetic particle at low temperature. The quantum tunneling rates for these processes are evaluated for two examples of macroscopic quantum tunneling and one example of macroscopic quantum coherence. The calculations are performed by using the two sublattice model and the instanton method in the spin coherent state path integral. Quantum interference or the spin parity effect is also discussed for each case.展开更多
A search was made for possible half-metallic(HM)antiferromagnet(AFM)in all the(C_(2)^(92)=406)double perovskites structures of Sr2BB′O6 where BB′pairs are any combination of 3d,4d or 5d transition elements with the ...A search was made for possible half-metallic(HM)antiferromagnet(AFM)in all the(C_(2)^(92)=406)double perovskites structures of Sr2BB′O6 where BB′pairs are any combination of 3d,4d or 5d transition elements with the exception of La.Sr can also be replaced by Ca or Ba whenever HM-AFM was found and similar calculations were then performed in order to probe further possibilities.It was found that A_(2)MoOsO_(6),A_(2)TcReO_(6),A_(2)CrRuO_(6),where A=Ca,Sr,Ba,are all potential candidates for HM-AFM.The AFM of A2BB′O6 comes from both the superexchange mechanism and the generalized double exchange mechanism via the B(t2g)-O2pp-B′(t2g)coupling,With the latter also being the origin of their HM.Also considered were the effects of spin-orbit coupling(SOC)and correlation(+U)by introducing+SOC and+U corrections.It is found that the SOC effect has much less influence than the correlation effect on the HMproperty of the compounds.For A_(2)TcReO_(6)and A_(2)CrRuO_(6),after+U,they become nearlyMott-Insulators.In the future,it is hoped that therewill be further experimental confirmation for these possible HM-AFMcandidates.展开更多
High-quality antiferromagnetic(AFM)θ-phase manganese nitride(MnN)films were successfully grown on MgO(001)substrates by plasma-assisted molecular beam epitaxy.Structural analysis confirms the high-quality MnN film ha...High-quality antiferromagnetic(AFM)θ-phase manganese nitride(MnN)films were successfully grown on MgO(001)substrates by plasma-assisted molecular beam epitaxy.Structural analysis confirms the high-quality MnN film has a tetragonal distortion with a c/a ratio of~0.98.The film exhibits exceptional stability in both aqueous and ambient conditions,which is a crucial factor for practical applications.Electrical transport reveals its metallic behavior with an upturn at low temperatures,which could be attributed to the Kondo effect originated from nitrogen vacancy-induced magnetic impurities.Room temperature exchange bias has been demonstrated in a MnN/CoFeB heterostructure,verifying the AFM ordering of MnN.Considering its high Néel temperature~650 K,superior stability,and low-cost,this work highlights the epitaxial MnN films as a promising candidate for AFM spintronic applications.展开更多
In this work,Ga-doped Ce RhIn_(5) single crystals are grown by In/Ga flux method.Single-crystal X-ray diffraction,magnetic susceptibility,specific heat,and neutron diffraction measurements are utilized to characterize...In this work,Ga-doped Ce RhIn_(5) single crystals are grown by In/Ga flux method.Single-crystal X-ray diffraction,magnetic susceptibility,specific heat,and neutron diffraction measurements are utilized to characterize the sample quality and the antiferromagnetic transition temperature T_(N).By substituting In with Ga,T_(N) is slightly decreased,but the antiferromagnetic transition peaks in magnetic susceptibility and specific heat measurements are obviously broadened by external field along c-axis.By comparing with Zn-doped Ce RhIn_(5),it can be concluded that T_(N) is dominated by electron density,and the stiffness of antiferromagnetic transition is obviously reduced by Ga substitution.The substitution effects of Ga are possibly caused by forming heterogeneous local structures,which avoids quantum critical point,superconductivity,and non-Fermi liquid states.Investigations on Gadoped Ce RhIn_(5) help to comprehend the chemical substitution effects in Ce RhIn_(5),and the interaction between heterogeneous structure and long-range antiferromagnetic states.展开更多
Multifunctional semiconductors play an important role in developing advanced photoelectric technologies.In this work,based on an octahedral replacement strategy in chalcogenides,a new selenide semiconductor NaMn_(3)Ga...Multifunctional semiconductors play an important role in developing advanced photoelectric technologies.In this work,based on an octahedral replacement strategy in chalcogenides,a new selenide semiconductor NaMn_(3)Ga_(3)Se_(8)was rationally designed,and synthesized by the flux method.The compound crystallizes in the noncentrosymmetric(NCS)P_(6)space group,and is composed of unique prismatic[NaSe_(6)],octahedral[MnSe_(6)]and tetrahedral[GaSe_(4)]motifs,inheriting the stable three-dimensional framework built by the octahedral and tetrahedral units in the A^(Ⅰ)Mg_(3)^(Ⅱ)C_(3)^(Ⅲ)Q_(8)^(Ⅵ)family.NaMn_(3)Ga_(3)Se_(8)shows the largest known secondary nonlinear optical(NLO)response of~2.1×AgGaS_(2)(AGS)in the A^(Ⅰ)Mg_(3)^(Ⅱ)C_(3)^(Ⅲ)Q_(8)^(Ⅵ)family,and a high laser-induced damage threshold of~3.0×AGS.Meanwhile,the introduction of Mn2t with unpaired 3d electrons induces a strong red emission band(685–805 nm)under the excitation source of 496 nm,as well as a paramagnetic to antiferromagnetic(AFM)transition at 7.3 K.The results confirm that NaMn_(3)Ga_(3)Se_(8)possesses multifunctional features including significant NLO response,fluorescence emission and AFM properties,and illustrate that replacing octahedral units with approaching size and geometry(like[MgSe_(6)]and[MnSe_(6)])could be a feasible way to develop multifunctional chalcogenides.展开更多
The ground-state magnetic ordering of uranium mononitride(UN)remains a contentious topic due to the unexpected lack of crystallographic distortion in the traditionally accepted 1k antiferromagnetic(AFM)state.This disc...The ground-state magnetic ordering of uranium mononitride(UN)remains a contentious topic due to the unexpected lack of crystallographic distortion in the traditionally accepted 1k antiferromagnetic(AFM)state.This discrepancy casts doubt on the validity of the 1k magnetic ordering of UN.Here,we investigate the crystal structure,high-pressure phase transitions,and dynamical and mechanical properties of UN in its 1k and 3k AFM ground states using density functional theory(DFT).Our results reveal that the undistorted 3k AFM state of Fm3m within the DFT+U+SOC scheme is more consistent with experimental results.The Hubbard U and spin-orbit coupling(SOC)are critical for accurately capturing the crystal structure,high-pressure structural phase transition,and dynamical properties of UN.In addition,we have identified a new high-pressure magnetic phase transition from the nonmagnetic(NM)phase of R3m to the P63/mmc AFM state.Electronic structure analysis reveals that the magnetic ordering in the ground state is primarily linked to variations in partial 5f orbital distributions.Our calculations provide valuable theoretical insights into the complex magnetic structures of a typical strongly correlated uranium-based compound.Moreover,they provide a framework for understanding other similar actinide systems.展开更多
We present a comprehensive investigation into the physical properties of intermetallic ErPd_(2)Si_(2),a compound renowned for its intriguing magnetic and electronic characteristics.We confirm the tetragonal crystal st...We present a comprehensive investigation into the physical properties of intermetallic ErPd_(2)Si_(2),a compound renowned for its intriguing magnetic and electronic characteristics.We confirm the tetragonal crystal structure of ErPd_(2)Si_(2)within the I4/mmm space group.Notably,we observed anisotropic thermal expansion,with the lattice constant a expanding and c contracting between 15 and300 K.This behaviour is attributed to lattice vibrations and electronic contributions.Heat capacity measurements revealed three distinct temperature regimes:T_(1)~3.0 K,T_(N)~4.20 K,and T_(2)~15.31 K.These correspond to thedisappearance of spin-density waves,the onset of an incommensurate antiferromagnetic(AFM)structure,and the crystal-field splitting and/or the presence of short-range spin fluctuations,respectively.Remarkably,the AFM phase transition anomaly was observed exclusively in lowfield magnetization data(120 Oe)at T_(N).A high magnetic field(B=3 T)effectively suppressed this anomaly,likely due to spin-flop and spin-flip transitions.Furthermore,the extracted effective paramagnetic(PM)moments closely matched the expected theoretical value,suggesting a dominant magnetic contribution from localized 4f spins of Er.Additionally,significant differences in resistance(R)values at low temperatures under applied B indicated a magnetoresistance(MR)effect with a minimum value of-4.36%.Notably,the measured MR effect exhibited anisotropic behavior,where changes in the strength or direction of the applied B induced variations in the MR effect.A twofold symmetry of R was discerned at 3 and9 T,originating from the orientation of spin moments relative to the applied B.Intriguingly,above T_(N),shortrange spin fluctuations also displayed a preferred orientation along the c-axis due to single-ion anisotropy.Moreover,the R demonstrated a clear B dependence below30 K.The magnetic-field point where R transitions from linear B dependence to a stable state increased with temperature:~3 T(at 2 K),~4.5 T(at 4 K),and~6 T(at 10 K).Our study sheds light on the magnetic and electronic properties of ErPd_(2)Si_(2),offering valuable insights for potential applications in spintronics and quantum technologies.展开更多
In antiferromagnets,dipolar coupling is often disregarded due to the cancellation of magnetic moments between the two sublattices,so that the spin-wave dispersion is predominantly determined by exchange interactions.H...In antiferromagnets,dipolar coupling is often disregarded due to the cancellation of magnetic moments between the two sublattices,so that the spin-wave dispersion is predominantly determined by exchange interactions.However,antiferromagnetic spin waves typically involve a slight misalignment of the magnetic moments on the sublattices,which gives rise to a small net magnetization enabling long-range dipolar coupling.In this paper,we investigate the role of dipolar coupling in spin-wave excitations and its influence on the resulting dispersion.Our findings show that:(i)when the Néel vector is perpendicular to the film plane or lies within the film plane and parallel to the wave vector,the dispersion branches can be divided into two groups:those unaffected by the dipolar field and those influenced by it.In these cases,the total magnetic moment remains linearly polarized,but the polarization directions differ between the two types of branches;(ii)when the Néel vector lies in the film plane and is perpendicular to the wave vector,the dipolar interactions affect both types of dispersion branches,leading to their hybridization.This hybridization alters the polarization of the magnetic moment,resulting in elliptical polarization.展开更多
Interlayer exchange coupling(IEC)plays a critical role in spin-orbit torque(SOT)switching in synthetic magnets.This work establishes a fundamental correlation between IEC and SOT dynamics within Co/Pt-based synthetic ...Interlayer exchange coupling(IEC)plays a critical role in spin-orbit torque(SOT)switching in synthetic magnets.This work establishes a fundamental correlation between IEC and SOT dynamics within Co/Pt-based synthetic antiferromagnets and synthetic ferromagnets.The antiferromagnetic and ferromagnetic coupling states are precisely engineered through Ruderman-Kittel-Kasuya-Yosida(RKKY)interactions by modulating the Ir spacer thickness.Experimental results reveal that the critical switching current density exhibits a strong positive correlation with the IEC strength,regardless of the coupling type.A comprehensive theoretical framework based on the Landau-Lifshitz-Gilbert equation elucidates how IEC contributes to the effective energy barrier that must be overcome during SOT-induced magnetization switching.Significantly,the antiferromagnetically coupled samples demonstrate enhanced SOT efficiency,with the spin Hall angle being directly proportional to the antiferromagnetic exchange coupling field.These insights establish a coherent physical paradigm for understanding IEC-dependent SOT dynamics and provide strategic design principles for the development of energy-efficient next-generation spintronic devices.展开更多
基金supported by the National Key Projects for Research and Development of China(Grant Nos.2021YFA1400400 and 2024YFA1408104)the National Natural Science Foundation of China(Grant Nos.12434005,12374137,and 92165205).
文摘We investigate the origin of the 1/3 magnetization plateau in the S=1/2 kagome antiferromagnetic Heisenberg model using the variational Monte Carlo and exact diagonalization methods,to account for the recent experimental observations in YCu_(3)(OH)_(6+x)Br_(3-x)and YCu_(3)(OD)_(6+x)Br_(3-x).We identify three degenerate valencebond-solid(VBS)states forming a√3×√3 unit cell.These states exhibit David-star patterns in the spin moment distribution with only two fractional values-1/3 and 2/3,and are related through translational transformations.While the spin correlations in these VBS states are found to be short-range,resembling a quantum spin liquid,we show that they have a vanishing topological entanglement entropy and thus are topologically trivial many-body states.Our theoretical results provide strong evidence that the 1/3 magnetization plateau observed in recent experiments arises from these√3×√3 VBS states with fractional spin moments.
文摘就Bethuel,Brezis和Helein提出的问题讨论了Planar Ferromagnets and Antiferromagnets泛函在H={u(x)=(sinf(r)|xx|,cosf(r))∈H1(B1,S2);f(0)=0,f(1)=2π,r=|x|}中的径向极小元的一些性质,其中包括此泛函的径向极小元的零点的分布及若干个上界估计,并给出了这一问题的肯定回答.
文摘A quantum spin liquid (QSL) is an exotic quantum ground state that does not break conventional symmetries and where the spins in the system remain dynamic down to zero temperature. Unlike a trivial paramagnetic state, it features long-range quantum entanglement and supports fractionalized excitations.
基金Supported by the National Natural Science Foundation of China (Grant Nos.51871235,51671212,52031014,51771198,and51801212)the National Key Research and Development Program of China (Grant Nos.2016YFA0300701,2017YFB0702702,and2017YA0206302)+2 种基金the Key Research Program of Frontier Sciences,CAS (Grant Nos.QYZDJ-SSW-JSC023,KJZD-SW-M01ZDYZ2012-2)support from the Natural Science Foundation for Distinguished Young Scholars of Hebei Province of China (S&T Program of Hebei,Grant No.A2019205310)。
文摘Magnon-magnon coupling in synthetic antiferromagnets advances it as hybrid magnonic systems to explore the quantum information technologies.To induce magnon-magnon coupling,the parity symmetry between two magnetization needs to be broken.Here we experimentally demonstrate a convenient method to break the parity symmetry by the asymmetric structure.We successfully introduce a magnon-magnon coupling in Ir-based synthetic antiferromagnets CoFeB(10 nm)/Ir(t_(Ir)=0.6 nm,1.2 nm)/CoFeB(13 nm).Remarkably,we find that the weakly uniaxial anisotropy field(-20 Oe)makes the magnon-magnon coupling anisotropic.The coupling strength presented by a characteristic anticrossing gap varies in the range between 0.54 GHz and 0.90 GHz for t_(Ir)=0.6 nm,and between 0.09 GHz and 1.4 GHz for t_(Ir)=1.2 nm.Our results demonstrate a feasible way to induce magnon-magnon coupling by an asymmetric structure and tune the coupling strength by varying the direction of in-plane magnetic field.The magnon-magnon coupling in this highly tunable material system could open exciting perspectives for exploring quantum-mechanical coupling phenomena.
基金Project supported by EPSRC(Grant No.EP/P019749/1)support from the Royal Society through a University Research Fellowship
文摘Antiferromagnets offer considerable potential for electronic device applications. This article reviews recent demonstrations of spin manipulation in antiferromagnetic devices using applied electrical currents. Due to spin–orbit coupling in environments with particular crystalline or structural symmetries, the electric current can induce an effective magnetic field with a sign that alternates on the lengthscale of the unit cell. The staggered effective field provides an efficient mechanism for switching antiferromagnetic domains and moving antiferromagnetic domain walls, with writing speeds in the terahertz regime.
基金Project supported by the Natural Science Foundation of Anhui Province,China(Grant Nos.2108085MA16 and2108085QA22)the Key Project of Anhui Provincial Department of Education(Grant No.KJ2020A0013)+1 种基金the Key Project of the Foundation of Anhui Education Committee,China(Grant No.2022AH050066)the National Natural Science Foundation of China(Grant Nos.U1832209,11874336,12274338,12104010,12104011,52102333,and 12004003)。
文摘To study the effects of lanthanide ions on the geometrically frustrated antiferromagnets and their magnetic properties,we grew high-quality single crystals of LnCu_(3)(OH)_(6)Br_(3)(Ln=Nd,Sm,and Eu)by hydrothermal method and studied their crystal structures and magnetic properties.The refinements of the crystal structure referred to the powder x-ray diffraction data show that LnCu_(3)(OH)_(6)Br_(3)adopt a Kapellasite-type layer structure,which is isostructural to their chlorine analogue.Magnetic susceptibilities demonstrate that LnCu_(3)(OH)_(6)Br_(3)have strong antiferromagnetic coupling and a pronounced magnetic frustration effect.Magnetization measurements indicate canted antiferromagnetic ordering of Cu^(2+)ions around 16 K within the kagoméplane and weak ferromagnetic coupling.Moreover,shoulder-like anomalies in specific heat around 16 K could be a signature of emergent of magnetic ordering.The low-temperature negative magnetization and specific heat of LnCu_(3)(OH)_(6)Br_(3)(Ln=Nd,Sm,and Eu)indicate that Ln^(3+)ions induce more exotic magnetic ground state properties.
基金Project supported by the Natural Science Foundation of Gansu Province, China (Grant No. 22JR5RA775)the Science and Technology Program of Lanzhou, China (Grant No. 2021-1-157)+2 种基金the Guangdong Basic and Applied Basic Research Foundation, China (Grant Nos. 2020A1515110998 and 2022A1515012123)the Outstanding Youth Foundation of Gansu Academy of Science, China (Grant No. 2021YQ01)the Innovative Team Construction Project of Gansu Academy of Sciences, China (Grant No. 2020CX005-01)。
文摘Perpendicular synthetic-antiferromagnet(p-SAF) has broad applications in spin-transfer-torque magnetic random access memory and magnetic sensors. In this study, the p-SAF films consisting of (Co/Ni)3]/Ir(tIr)/[(Ni/Co)3are fabricated by magnetron sputtering technology. We study the domain structure and switching field distribution in p-SAF by changing the thickness of the infrared space layer. The strongest exchange coupling field(Hex) is observed when the thickness of Ir layer(tIr) is 0.7 nm and becoming weak according to the Ruderman–Kittel–Kasuya–Yosida-type coupling at 1.05 nm,2.1 nm, 4.55 nm, and 4.9 nm in sequence. Furthermore, the domain switching process between the upper Co/Ni stack and the bottom Co/Ni stack is different because of the antiferromagnet coupling. Compared with ferromagnet coupling films, the antiferromagnet samples possess three irreversible reversal regions in the first-order reversal curve distribution.With tIrincreasing, these irreversible reversal regions become denser and smaller. The results from this study will help us understand the details of the magnetization reversal process in the p-SAF.
基金the support of the startup funds at HFNLthe Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302800)+3 种基金Anhui Initiative in Quantum Information Technologies(Grant No.AHY170000)supported by the start-up of Zhejiang Universitythe Fundamental Research Funds for the Central Universities(Grant No.226-2024-00068)funded by the Jane and Aatos Erkko Foundation and the Keele Foundation as part of the SuperC collaboration。
文摘Unconventional antiferromagnets(AFMs)with non-relativistic spin-splitting,such as the recently discovered altermagnet,have recently gained significant interest due to their potential for novel quantum phenomena and spintronic applications.The compensated magnetization in unconventional AFMs is protected by spin-space symmetries.In this work,we explore the symmetrybreaking effects and identify three distinct mechanisms for inducing net spin magnetizations in unconventional AFMs with collinear or non-collinear spins:(1)finite size effect,(2)extrinsic spin canting effect,and(3)irradiation with circularly polarized light.We show that the induced spin magnetizations are controllable and manifest as diverse intriguing phenomena.For the finite size system,the confined direction of a two-dimensional AM creates quantum-well-like subbands that determine the spin magnetization.This effect can be experimentally probed by measuring the spin density of states and the spin-polarization of Andreev-bound states within planar Josephson junctions.In the case of spin canting effect,it leads to peculiar anisotropic and non-monotonic behaviors in the superconducting proximity effect.Lastly,with circularly polarized light,spin magnetization is driven by the polarized light and the chirality of non-collinear magnetic order,thus offering a direct means of detecting the chirality of magnetic order in real materials.Our findings provide valuable insight into understanding and probing the spin magnetization in unconventional AFM materials.
基金supported by the Natural Science Foundation of China(No.19971030)the Natural Science Foundation of Guangdong(No.000671,No.031495)
文摘In this paper,the global existence and uniqueness of a smooth solution to the periodic initial-value problem of the spin equations of antiferromagnets in 1 dimension are proved.
文摘Exotic quantum spin liquid (QSL) states and fractionalized quasiparticles in frustrated magnets are of much current interest in theoretical and experimental studies of quantum magnetism. The kagome-lattice Heisenberg antiferromagnet (KAFM) provides a possible realization of just such novel topological states of matter. The kagome lattice shown in Fig. 1 is one of eleven Archimedean lattices in two spatial dimensions, where the word kagome itself means uweave pattera" in Japanese.
基金supported by the National Natural Science Foundation of China(Grant Nos.51671110,and 51871130)。
文摘Ferromagnets play an important role in our daily lives,in such common devies as:compasses,electric motors and hard disks.For a long time,the antiferromagnetic(AFM)materials have been ignored for the applications.Even the Nobel laureate L.Néel said that antiferromagnets are interesting,but useless.
文摘The tunneling behavior of the Néel vector out of metastable easy directions or between degenerate easy directions is studied for a small single\|domain antiferromagnetic particle at low temperature. The quantum tunneling rates for these processes are evaluated for two examples of macroscopic quantum tunneling and one example of macroscopic quantum coherence. The calculations are performed by using the two sublattice model and the instanton method in the spin coherent state path integral. Quantum interference or the spin parity effect is also discussed for each case.
基金supports received from the National Science Council(99B0320)the National Center for Theoretical Sciences(NCTS),South Taiwan.
文摘A search was made for possible half-metallic(HM)antiferromagnet(AFM)in all the(C_(2)^(92)=406)double perovskites structures of Sr2BB′O6 where BB′pairs are any combination of 3d,4d or 5d transition elements with the exception of La.Sr can also be replaced by Ca or Ba whenever HM-AFM was found and similar calculations were then performed in order to probe further possibilities.It was found that A_(2)MoOsO_(6),A_(2)TcReO_(6),A_(2)CrRuO_(6),where A=Ca,Sr,Ba,are all potential candidates for HM-AFM.The AFM of A2BB′O6 comes from both the superexchange mechanism and the generalized double exchange mechanism via the B(t2g)-O2pp-B′(t2g)coupling,With the latter also being the origin of their HM.Also considered were the effects of spin-orbit coupling(SOC)and correlation(+U)by introducing+SOC and+U corrections.It is found that the SOC effect has much less influence than the correlation effect on the HMproperty of the compounds.For A_(2)TcReO_(6)and A_(2)CrRuO_(6),after+U,they become nearlyMott-Insulators.In the future,it is hoped that therewill be further experimental confirmation for these possible HM-AFMcandidates.
文摘High-quality antiferromagnetic(AFM)θ-phase manganese nitride(MnN)films were successfully grown on MgO(001)substrates by plasma-assisted molecular beam epitaxy.Structural analysis confirms the high-quality MnN film has a tetragonal distortion with a c/a ratio of~0.98.The film exhibits exceptional stability in both aqueous and ambient conditions,which is a crucial factor for practical applications.Electrical transport reveals its metallic behavior with an upturn at low temperatures,which could be attributed to the Kondo effect originated from nitrogen vacancy-induced magnetic impurities.Room temperature exchange bias has been demonstrated in a MnN/CoFeB heterostructure,verifying the AFM ordering of MnN.Considering its high Néel temperature~650 K,superior stability,and low-cost,this work highlights the epitaxial MnN films as a promising candidate for AFM spintronic applications.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFA1402203)the National Natural Science Foundations of China(Grant Nos.12174065 and 12104424)the Shanghai Municipal Science and Technology(Grant No.2019SHZDZX01)。
文摘In this work,Ga-doped Ce RhIn_(5) single crystals are grown by In/Ga flux method.Single-crystal X-ray diffraction,magnetic susceptibility,specific heat,and neutron diffraction measurements are utilized to characterize the sample quality and the antiferromagnetic transition temperature T_(N).By substituting In with Ga,T_(N) is slightly decreased,but the antiferromagnetic transition peaks in magnetic susceptibility and specific heat measurements are obviously broadened by external field along c-axis.By comparing with Zn-doped Ce RhIn_(5),it can be concluded that T_(N) is dominated by electron density,and the stiffness of antiferromagnetic transition is obviously reduced by Ga substitution.The substitution effects of Ga are possibly caused by forming heterogeneous local structures,which avoids quantum critical point,superconductivity,and non-Fermi liquid states.Investigations on Gadoped Ce RhIn_(5) help to comprehend the chemical substitution effects in Ce RhIn_(5),and the interaction between heterogeneous structure and long-range antiferromagnetic states.
基金supported by the Natural Science Foundation of the Xinjiang Uygur Autonomous Region(2024D01E30)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0880000)+1 种基金the Open Fund of the Anhui Key Laboratory of Photonic Materials and Devices(AHKL2024KF02)the National Natural Science Foundation of China(22475234,22335007,22193044 and 22361132544).
文摘Multifunctional semiconductors play an important role in developing advanced photoelectric technologies.In this work,based on an octahedral replacement strategy in chalcogenides,a new selenide semiconductor NaMn_(3)Ga_(3)Se_(8)was rationally designed,and synthesized by the flux method.The compound crystallizes in the noncentrosymmetric(NCS)P_(6)space group,and is composed of unique prismatic[NaSe_(6)],octahedral[MnSe_(6)]and tetrahedral[GaSe_(4)]motifs,inheriting the stable three-dimensional framework built by the octahedral and tetrahedral units in the A^(Ⅰ)Mg_(3)^(Ⅱ)C_(3)^(Ⅲ)Q_(8)^(Ⅵ)family.NaMn_(3)Ga_(3)Se_(8)shows the largest known secondary nonlinear optical(NLO)response of~2.1×AgGaS_(2)(AGS)in the A^(Ⅰ)Mg_(3)^(Ⅱ)C_(3)^(Ⅲ)Q_(8)^(Ⅵ)family,and a high laser-induced damage threshold of~3.0×AGS.Meanwhile,the introduction of Mn2t with unpaired 3d electrons induces a strong red emission band(685–805 nm)under the excitation source of 496 nm,as well as a paramagnetic to antiferromagnetic(AFM)transition at 7.3 K.The results confirm that NaMn_(3)Ga_(3)Se_(8)possesses multifunctional features including significant NLO response,fluorescence emission and AFM properties,and illustrate that replacing octahedral units with approaching size and geometry(like[MgSe_(6)]and[MnSe_(6)])could be a feasible way to develop multifunctional chalcogenides.
基金supported by the National Natural Science Foundation of China(Grant Nos.12204482 and U2430211)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(Grant No.2020L0537)the Fundamental Research Program of Shanxi Province(Grant No.202103021224250)the Hainan Provincial Natural Science Foundation of China(Grant No.225MS076).
文摘The ground-state magnetic ordering of uranium mononitride(UN)remains a contentious topic due to the unexpected lack of crystallographic distortion in the traditionally accepted 1k antiferromagnetic(AFM)state.This discrepancy casts doubt on the validity of the 1k magnetic ordering of UN.Here,we investigate the crystal structure,high-pressure phase transitions,and dynamical and mechanical properties of UN in its 1k and 3k AFM ground states using density functional theory(DFT).Our results reveal that the undistorted 3k AFM state of Fm3m within the DFT+U+SOC scheme is more consistent with experimental results.The Hubbard U and spin-orbit coupling(SOC)are critical for accurately capturing the crystal structure,high-pressure structural phase transition,and dynamical properties of UN.In addition,we have identified a new high-pressure magnetic phase transition from the nonmagnetic(NM)phase of R3m to the P63/mmc AFM state.Electronic structure analysis reveals that the magnetic ordering in the ground state is primarily linked to variations in partial 5f orbital distributions.Our calculations provide valuable theoretical insights into the complex magnetic structures of a typical strongly correlated uranium-based compound.Moreover,they provide a framework for understanding other similar actinide systems.
基金supported by the Science and Technology Development Fund,Macao SAR,China(File Nos.0090/2021/A2 and 0104/2024/AFJ)University of Macao(MYRG-GRG2024-00158-IAPME)+3 种基金the support from the National Natural Science Foundation of China(No.52275467)the support from the National Natural Science Foundation of China(No.52271037)Shaanxi Provincial Natural Science Fundamental Research Program,China(No.2023-JC-ZD-23)the Fundamental Research Funds for the Central Universities of China(No.D5000240307)
文摘We present a comprehensive investigation into the physical properties of intermetallic ErPd_(2)Si_(2),a compound renowned for its intriguing magnetic and electronic characteristics.We confirm the tetragonal crystal structure of ErPd_(2)Si_(2)within the I4/mmm space group.Notably,we observed anisotropic thermal expansion,with the lattice constant a expanding and c contracting between 15 and300 K.This behaviour is attributed to lattice vibrations and electronic contributions.Heat capacity measurements revealed three distinct temperature regimes:T_(1)~3.0 K,T_(N)~4.20 K,and T_(2)~15.31 K.These correspond to thedisappearance of spin-density waves,the onset of an incommensurate antiferromagnetic(AFM)structure,and the crystal-field splitting and/or the presence of short-range spin fluctuations,respectively.Remarkably,the AFM phase transition anomaly was observed exclusively in lowfield magnetization data(120 Oe)at T_(N).A high magnetic field(B=3 T)effectively suppressed this anomaly,likely due to spin-flop and spin-flip transitions.Furthermore,the extracted effective paramagnetic(PM)moments closely matched the expected theoretical value,suggesting a dominant magnetic contribution from localized 4f spins of Er.Additionally,significant differences in resistance(R)values at low temperatures under applied B indicated a magnetoresistance(MR)effect with a minimum value of-4.36%.Notably,the measured MR effect exhibited anisotropic behavior,where changes in the strength or direction of the applied B induced variations in the MR effect.A twofold symmetry of R was discerned at 3 and9 T,originating from the orientation of spin moments relative to the applied B.Intriguingly,above T_(N),shortrange spin fluctuations also displayed a preferred orientation along the c-axis due to single-ion anisotropy.Moreover,the R demonstrated a clear B dependence below30 K.The magnetic-field point where R transitions from linear B dependence to a stable state increased with temperature:~3 T(at 2 K),~4.5 T(at 4 K),and~6 T(at 10 K).Our study sheds light on the magnetic and electronic properties of ErPd_(2)Si_(2),offering valuable insights for potential applications in spintronics and quantum technologies.
基金supported by the National Natural Science Foundation of China(Grant No.12474110)the National Key Research and Development Program of China(Grant No.2022YFA1403300)+1 种基金the Innovation Program for Quantum Science and Technology(Grant No.2024ZD0300103)the Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)。
文摘In antiferromagnets,dipolar coupling is often disregarded due to the cancellation of magnetic moments between the two sublattices,so that the spin-wave dispersion is predominantly determined by exchange interactions.However,antiferromagnetic spin waves typically involve a slight misalignment of the magnetic moments on the sublattices,which gives rise to a small net magnetization enabling long-range dipolar coupling.In this paper,we investigate the role of dipolar coupling in spin-wave excitations and its influence on the resulting dispersion.Our findings show that:(i)when the Néel vector is perpendicular to the film plane or lies within the film plane and parallel to the wave vector,the dispersion branches can be divided into two groups:those unaffected by the dipolar field and those influenced by it.In these cases,the total magnetic moment remains linearly polarized,but the polarization directions differ between the two types of branches;(ii)when the Néel vector lies in the film plane and is perpendicular to the wave vector,the dipolar interactions affect both types of dispersion branches,leading to their hybridization.This hybridization alters the polarization of the magnetic moment,resulting in elliptical polarization.
基金Project supported by the“Pioneer”and“Leading Goose”R&D Program of Zhejiang Province(Grant No.2022C01053)the Key Research and Development Program of Zhejiang Province(Grant No.2021C01039)+1 种基金the National Natural Science Foundation of China(Grant No.62293493)the Natural Science Foundation of Zhejiang Province,China(Grant No.LQ21A050001)。
文摘Interlayer exchange coupling(IEC)plays a critical role in spin-orbit torque(SOT)switching in synthetic magnets.This work establishes a fundamental correlation between IEC and SOT dynamics within Co/Pt-based synthetic antiferromagnets and synthetic ferromagnets.The antiferromagnetic and ferromagnetic coupling states are precisely engineered through Ruderman-Kittel-Kasuya-Yosida(RKKY)interactions by modulating the Ir spacer thickness.Experimental results reveal that the critical switching current density exhibits a strong positive correlation with the IEC strength,regardless of the coupling type.A comprehensive theoretical framework based on the Landau-Lifshitz-Gilbert equation elucidates how IEC contributes to the effective energy barrier that must be overcome during SOT-induced magnetization switching.Significantly,the antiferromagnetically coupled samples demonstrate enhanced SOT efficiency,with the spin Hall angle being directly proportional to the antiferromagnetic exchange coupling field.These insights establish a coherent physical paradigm for understanding IEC-dependent SOT dynamics and provide strategic design principles for the development of energy-efficient next-generation spintronic devices.
