Altermagnetism,a recently identified class of collinear magnetism,combines key features of antiferromagnets and ferromagnets.Despite having zero net magnetization,altermagnetic materials exhibit anomalous transport ef...Altermagnetism,a recently identified class of collinear magnetism,combines key features of antiferromagnets and ferromagnets.Despite having zero net magnetization,altermagnetic materials exhibit anomalous transport effects,including the anomalous Hall,Nernst,and thermal Hall effects,as well as magneto-optical Kerr and Faraday effects.These phenomena,previously thought unique to ferromagnets,are dictated by symmetry,as confirmed by density functional theory(DFT)calculations.However,an effective model-based approach to verify these symmetry constraints remains unavailable.In this Letter,we construct a k·ρ model for d-wave altermagnets CuX_(2)(X=F,Cl)using spin space group representations and apply it to calculate the anomalous Hall effect.The symmetry-imposed transport properties predicted by the model are in agreement with the DFT results,providing a foundation for further investigation into symmetry-restricted transport phenomena in altermagnetic materials.展开更多
We investigate the possible Josephson diode effect(JDE)in a two-dimensional(2D)nonmagnetic planar s-wave superconductor junction,which is constructed on a spin-collinear d-wave altermagnet(AM)material in the presence ...We investigate the possible Josephson diode effect(JDE)in a two-dimensional(2D)nonmagnetic planar s-wave superconductor junction,which is constructed on a spin-collinear d-wave altermagnet(AM)material in the presence of Rashba spin-orbit interaction.It is demonstrated that the JDE is critically dependent on the crystalline axis of the AM relative to the current direction.The d_(x^(2)-y^(2))magnetization symmetry can support a JDE whereas the dxy symmetry does not facilitate it.The JDE efficiency can reach up to 40%and can be adjusted by an additional asymmetric gate voltage applied to the non-superconducting region of the junction,including control of its polarity.Our findings provide an electrical means to control the JDE within a non-magnetic AM-based superconducting junction.展开更多
Altermagnets represent a newly discovered class of magnetically ordered materials.Among all the candidates,CrSb stands out due to its largest spin splitting energy and highest Néel temperature exceeding 700 K,mak...Altermagnets represent a newly discovered class of magnetically ordered materials.Among all the candidates,CrSb stands out due to its largest spin splitting energy and highest Néel temperature exceeding 700 K,making it promising for room-temperature spintronic applications.Here we have successfully grown high quality CrSb(100)thin film on GaAs(110)substrate by molecular beam epitaxy.Using angle-resolved photoemission spectroscopy,we successfully obtained the three-dimensional electronic structure of the thin film.Moreover,we observed the emergence of the altermagnetic splitting bands corresponding to the calculated results along the low symmetry pathsT-QandP-D.The bands near the Fermi level are only spin splitting bands along theP-Ddirection,with splitting energy reaching as high as 910 meV.This finding provides insights into the magnetic properties of CrSb thin films and paves the way for further studies on their electronic structure and potential applications in spintronics.展开更多
Unconventional antiferromagnetism dubbed as altermagnetism was first discovered in rutile structured magnets,which is featured by spin splitting even without the spin–orbital coupling effect.This interesting phenomen...Unconventional antiferromagnetism dubbed as altermagnetism was first discovered in rutile structured magnets,which is featured by spin splitting even without the spin–orbital coupling effect.This interesting phenomenon has been discovered in more altermagnetic materials.In this work,we explore two-dimensional altermagnetic materials by studying two series of two-dimensional magnets,including MF4 with M covering all 3d and 4d transition metal elements,as well as TS2 with T=V,Cr,Mn,Fe.Through the magnetic symmetry operation of RuF4 and MnS2,it is verified that breaking the time inversion is a necessary condition for spin splitting.Based on symmetry analysis and first-principles calculations,we find that the electronic bands and magnon dispersion experience alternating spin splitting along the same path.This work paves the way for exploring altermagnetism in two-dimensional materials.展开更多
Two-dimensional planar pentagonal crystals,long pursued for their geometrically frustrated lattice configurations and emergent quantum phenomena,have remained challenging to realize due to the intrinsic incompatibilit...Two-dimensional planar pentagonal crystals,long pursued for their geometrically frustrated lattice configurations and emergent quantum phenomena,have remained challenging to realize due to the intrinsic incompatibility of regular pentagons with Euclidean tiling.Here,we unveil 37 dynamically stable binary planar pentagonal monolayers through high-throughput computational screening of 1470 stoichiometric candidates.These materials exhibit room-temperature magnetism,including ferromagnetic(Curie temperature(T_(C))up to 521 K),antiferromagnetic(Néel temperature(T_(N))up to 761 K),and altermagnetic(TN=984 K)ground states,alongside unprecedented electronic states:Dirac semimetals,Dirac half-metal,nodal-loop semimetal,nodal-loop half-metal,and altermagnetic semiconductors(Mn_(4)N_(2))with giant spin splitting(0.78 eV).The latter achieves pure spin-polarized transport windows(-0.04 to 0.36 eV)and strain-tunable valley splitting(18.2 meV under 4%uniaxial strain).Intrinsic type-Ⅱ multiferroicity emerges in Fe_(4)C_(2) and Mn_(4)C_(2),featuring in-plane electric polarization(1.4 and 1.6 pC/m),ferroelasticity(0.8%and 1.2%reversible strain),and reversal chirality.Topological band analysis identifies chiral edge states in Dirac semimetal pentagons,alongside a magnetic topological insulator with Chern number|C|=2 in Mo_(2)S_(4) and W_(2)Te_(4).Temperature-driven structural transitions in Os_(2)S_(4) and Tc_(2)S_(4) from pentagonal to Lieb lattices accompany topological state switching and metal-to-semiconductor transitions.This work establishes pentagonal lattices as a platform for symmetry-driven multifunctionality,bridging geometric frustration with applications in spintronics,nanoelectronics,and quantum devices.展开更多
Recently,the altermagnets,a new kind of collinear antiferromagnet with nearly zero net magnetization and momentumdependent spin-splitting of bands,have sparked great interest.Despite simple magnetic structures,these a...Recently,the altermagnets,a new kind of collinear antiferromagnet with nearly zero net magnetization and momentumdependent spin-splitting of bands,have sparked great interest.Despite simple magnetic structures,these altermagnets exhibit intriguing and intricate dependence of anomalous Hall effect(AHE)on the Néel vector,in contrast to the conventional perpendicular configuration of Hall current with magnetization in ferromagnets.However,the fundamental relationship between the AHE and the Néel vector remains largely elusive.Here,we reveal all the unconventional anomalous Hall textures in the Néel vector space,dubbed anomalous-Hall Néel textures(AHNTs)for altermagnets.Specifically,we identify 10 types across four categories of AHNTs for all altermagnets.Notably,we find that AHNTs resemble the known spin textures in momentum space and further reveal their symmetry origin.Meanwhile,we examine our key discoveries in prototypical altermagnets.Our work offers a thorough understanding of AHE in altermagnets and a complete and pictorial classification of altermagnets based on the geometry of response functions.展开更多
Altermagnets,with spin splitting and vanishing magnetization,have been attributed to many fascinating phenomena and potential applications.In particular,integrating ferroelectricity with altermagnetism to enable magne...Altermagnets,with spin splitting and vanishing magnetization,have been attributed to many fascinating phenomena and potential applications.In particular,integrating ferroelectricity with altermagnetism to enable magnetoelectric coupling and electric control of spin has drawn significant attention.However,its experimental realization and precise spin manipulation remain elusive.Here,by focusing on molecular ferroelectrics,the first discovered ferroelectrics renowned for their highly controllable molecular polarizations and structural flexibility,we reveal that these obstacles can be removed by an emergent multiferroic altermagnet with tunable spin polarization in a large class of fabricated organic materials.Using a symmetry-based design and a tight-binding model,we uncover the underlying mechanism of such molecular ferroelectric altermagnets and demonstrate how noncollinear molecular polarization can switch the spin polarization on and off and even reverse its sign,as detectable by the magneto-optical Kerr effect.From the first-principles calculations,we verify the feasibility of these materials in a series of well-established hybrid organic-inorganic perovskites and metal-organic frameworks.Our findings bridge molecular ferroelectrics and altermagnetic spintronics,highlighting an unexplored potential of multifunctional organic multiferroics.展开更多
Altermagnets—recognized among the Science Breakthroughs of the Year 2024—have rapidly emerged as a new frontier,unifying the zero net magnetization of antiferromagnets with the spin polarization of ferromagnets[1-3]...Altermagnets—recognized among the Science Breakthroughs of the Year 2024—have rapidly emerged as a new frontier,unifying the zero net magnetization of antiferromagnets with the spin polarization of ferromagnets[1-3].They are widely regarded as promising candidates for next-generation spintronics,yet the critical challenge of realizing precise,low-power electrical control of spin continues to draw intense attention[4-7].展开更多
Altermagnetic materials have recently attracted significant attention due to their unique intrinsic crystal symmetry.Breaking the lattice symmetry can yield a non-negligible piezomagnetic effect,which refers to a line...Altermagnetic materials have recently attracted significant attention due to their unique intrinsic crystal symmetry.Breaking the lattice symmetry can yield a non-negligible piezomagnetic effect,which refers to a linear relationship between strain and magnetization.We proposed a method based onε_(xz)andε_(xy)shear strains that induced additional spin splitting along band paths that were originally spin-degenerate and generated weak ferromagnetic moments in altermagnetic CoF_(2)and RuO_(2).Additionally,the signs of spin splitting and weak ferromagnetic moments were switched by reversing the shear strain direction.The weak ferromagnetism had a substantial contribution from the orbital magnetic moments,with its y(z)component associated with the charge quadrupole moment.Our study highlights that shear strain provides a novel approach for exploring the physical properties of spin splitting,piezomagnetism,and multipolar order,while also broadening avenues for tuning the properties of altermagnetic materials.展开更多
Spintronics exploits magnetic order parameters to encode binary information and utilizes spin-dependent transport for data processing[1].To date,most spintronic devices have been based on ferromagnetic materials,which...Spintronics exploits magnetic order parameters to encode binary information and utilizes spin-dependent transport for data processing[1].To date,most spintronic devices have been based on ferromagnetic materials,which offer straightforward information writing and reading through manipulation and detection of their magnetization.A prototypical device is the magnetic tunnel junction(MTJ),where non-volatile memory readout is achieved via the tunneling magnetoresistance(TMR)effect—distinct resistance states arising from parallel and antiparallel alignments of ferromagnetic electrodes.MTJs serve as the building blocks of magnetic random-access memories(MRAMs),which have already found commercial applications.展开更多
According to recent studies on sliding/moire ferroelectricity,most 2D van der Waals nonferroelectric monolayers can become ferroelectric via multilayer stacking.In this paper,we propose that a similar strategy can be ...According to recent studies on sliding/moire ferroelectricity,most 2D van der Waals nonferroelectric monolayers can become ferroelectric via multilayer stacking.In this paper,we propose that a similar strategy can be used to induce desirable van der Waals altermagnetism with symmetry-compensated collinear magnetic orders and non-relativistic spin splitting.Our first-principles calculations show the pervasive co-existence of sliding ferroelectricity and altermagnetism in a series of magnetic multilayers with antiparallel stacking configurations.Upon a twist angle in bilayers,moire ferroelectricity can be combined with altermagnetism,while some untwisted bilayers with zero net magnetizations exhibit non-relativistic spin splittings coupled with sliding ferroelectricity.Our study significantly expands the scope of altermagnetism,and its combination with sliding/moire ferroelectricity brings in new physics as well as promising applications,which should stimulate further experimental efforts.展开更多
ABN_(3)-type nitride perovskites offer a rich platform for multifunctional materials but remain synthetically elusive.Here,we develop a machine learning(ML)-guided framework to expand the library of nitride perovskite...ABN_(3)-type nitride perovskites offer a rich platform for multifunctional materials but remain synthetically elusive.Here,we develop a machine learning(ML)-guided framework to expand the library of nitride perovskites and identify multiferroic candidates.By integrating positive-unlabeled(PU)learning with crystal graph convolutional neural networks(CGCNN),we screen 1465 ABN_(3)compositions and predict 96 synthesizable compounds.Further symmetry and magnetic filtering yield 4 altermagnetic ferroelectric(AM-FE)perovskites.Among them,CeCrN_(3)emerges as a promising candidate,exhibiting a bandgap of 0.30 eV,a spontaneous polarization of 0.59μC/cm^(2),a high Curie temperature of 650 K,and a low polarization switching barrier of 53 meV,as confirmed by density functional theory(DFT)calculations.In addition,CeCrN_(3)demonstrates a pronounced bulk photovoltaic effect(BPVE),with the shift current reaching 44μA/V^(2)and an injection current reaching 2.4×10^(9)A/V^(2),both of which reverse upon FE switching.These findings not only advance the understanding of nitride perovskites but also provides a validated ML-DFT framework to guide experimental efforts in realizing novel functional materials.展开更多
Altermagnetism emerges as the third fundamental collinear magnetism recently.Associating nontrivial topology and quantum orders to this newly established magnetism is an important physical topic and may lead to intere...Altermagnetism emerges as the third fundamental collinear magnetism recently.Associating nontrivial topology and quantum orders to this newly established magnetism is an important physical topic and may lead to interesting physics such as unusual quantum spin Hall effect with time-reversal-symmetry breaking,topological superconductivity and spin-valley locking.Here,we first generalize the spinless Haldane model from the usual honeycomb lattice to the otherwise simpler square lattice.We then restore the doublet spin degree of freedom,the resulted spinful model resembles the Kane-Mele model and is able to describe the unprecedented physics which intertwine C-paired spin-valley locking,Dirac physics,nontrivial band topology and altermagnetism.Our works shed lights on future studies and applications in spintronics and valleytronics for altermagnetic materials,the lattice theories developed in this article may also find their broad applications to optical lattice with ultra cold atoms,photonic lattice,etc.other than the usual electronic systems.展开更多
The growing demand for artificial intelligence and complex computing has underscored the urgent need for advanced data storage technologies.Spin-orbit torque(SOT)has emerged as a leading candidate for high-speed,high-...The growing demand for artificial intelligence and complex computing has underscored the urgent need for advanced data storage technologies.Spin-orbit torque(SOT)has emerged as a leading candidate for high-speed,high-density magnetic random-access memory due to its ultrafast switching speed and low power consumption.This review systematically explores the generation and switching mechanisms of electron-mediated torques(including both conventional SOTs and orbital torques)and magnon-mediated torques.We discuss key materials that enable these effects:heavy metals,topological insulators,low-crystal-symmetry materials,non-collinear antiferromagnets,and altermagnets for conventional SOTs;3d,4d,and 5d transition metals for orbital torques;and antiferromagnetic insulator Ni O-and multiferroic Bi Fe O_(3)-based sandwich structures for magnon torques.We emphasize that although key components of SOT devices have been demonstrated,numerous promising materials and critical questions regarding their underlying mechanisms remain to be explored.Therefore,this field represents a dynamic and rapidly evolving frontier in spintronics,offering significant potential for advancing next-generation information storage and computational technologies.展开更多
Unconventional magnetism,including altermagnetism and unconventional compensated magnetism,characterized by its duality of real-space antiferromagnetic alignment and momentum-space spin splitting,has garnered widespre...Unconventional magnetism,including altermagnetism and unconventional compensated magnetism,characterized by its duality of real-space antiferromagnetic alignment and momentum-space spin splitting,has garnered widespread attention.While altermagnetism has been extensively studied,research on unconventional compensated magnetism remains very rare.In particular,unconventional compensated magnetic materials are only theoretically predicted and have not yet been synthesized experimentally.In this study,based on symmetry analysis and frst-principles electronic structure calculations,we predict that LaMn_(2)SbO_(6)is an unconventional compensated magnetic semiconductor.Given that the Mn ions at opposite spin lattice cannot be connected by any symmetry,the spin splitting in LaMn_(2)SbO_(6)is isotropic.More importantly,LaMn_(2)SbO_(6)has already been synthesized experimentally,and its magnetic structure has been confrmed by neutron scattering experiments.Therefore,LaMn_(2)SbO_(6)serves as an excellent material platform for investigating the novel physical properties of unconventional compensated magnetic materials.展开更多
Manipulating the spin and valley degrees of freedom of electrons is crucial for next-generation information technologies.Altermagnets,as an emerging magnetic phase,provide a quantum platform with intrinsic spin-valley...Manipulating the spin and valley degrees of freedom of electrons is crucial for next-generation information technologies.Altermagnets,as an emerging magnetic phase,provide a quantum platform with intrinsic spin-valley locking,enabling multi-state manipulation of both spin and valley.Here,we propose a Janus monolayer CaCoFeN_(2),achieved through in situ substitution of magnetic transition metal atoms in the two-dimensional(2D)altermagnet Ca(CoN)2[Phys.Rev.Lett.133,056401(2024)].Our first-principles calculations identify CaCoFeN_(2) as an anisotropic spin-plasmon ferrovalley semiconductor,with a large valley splitting of 273 meV solely through crystal symmetry breaking,without any involvement of spin-orbit coupling(SOC).Furthermore,its anisotropic electronic structures facilitate highly directional spin plasmon propagation.Carrier-type switching(n-type↔ptype)reverses the anisotropy along orthogonal axes,yielding open equi-frequency contours in n-type CaCoFeN_(2).The integration of spontaneous spin and valley polarization within a single material without SOC,offers new opportunities for advancements in spintronics and valleytronics.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.12274117)the Natural Science Foundation of Henan(Grant No.242300421214)+4 种基金the Program for Innovative Research Team(in Science and Technology)in the University of Henan Province(Grant No.24IRTSTHN025)the Open Fund of Guangdong Provincial Key Laboratory of Nanophotonic Manipulation(No.202502)Guangdong S&T Program(No.2023B1212010008)the High-Performance Computing Center of Henan Normal Universitysupported by the U.S.DOE,Office of Science(Grant No.DE-FG02-05ER46237)。
文摘Altermagnetism,a recently identified class of collinear magnetism,combines key features of antiferromagnets and ferromagnets.Despite having zero net magnetization,altermagnetic materials exhibit anomalous transport effects,including the anomalous Hall,Nernst,and thermal Hall effects,as well as magneto-optical Kerr and Faraday effects.These phenomena,previously thought unique to ferromagnets,are dictated by symmetry,as confirmed by density functional theory(DFT)calculations.However,an effective model-based approach to verify these symmetry constraints remains unavailable.In this Letter,we construct a k·ρ model for d-wave altermagnets CuX_(2)(X=F,Cl)using spin space group representations and apply it to calculate the anomalous Hall effect.The symmetry-imposed transport properties predicted by the model are in agreement with the DFT results,providing a foundation for further investigation into symmetry-restricted transport phenomena in altermagnetic materials.
基金supported by the National Natural Science Foundation of China(Grant No.12174051)the Fundamental Research Funds for Central Universities。
文摘We investigate the possible Josephson diode effect(JDE)in a two-dimensional(2D)nonmagnetic planar s-wave superconductor junction,which is constructed on a spin-collinear d-wave altermagnet(AM)material in the presence of Rashba spin-orbit interaction.It is demonstrated that the JDE is critically dependent on the crystalline axis of the AM relative to the current direction.The d_(x^(2)-y^(2))magnetization symmetry can support a JDE whereas the dxy symmetry does not facilitate it.The JDE efficiency can reach up to 40%and can be adjusted by an additional asymmetric gate voltage applied to the non-superconducting region of the junction,including control of its polarity.Our findings provide an electrical means to control the JDE within a non-magnetic AM-based superconducting junction.
基金supported by the National Key R&D Program of China[Grant No.2023YFA1406304(J J)]the National Natural Science Foundation of China[Grant No.12174362(J J)]+2 种基金the Innovation Program for Quantum Science and Technology[Grant No.2021ZD0302803(D L F)]the New Cornerstone Science Foundation(D L F)Beamline 03U of the Shanghai Synchrotron Radiation Facility,which is supported by ME2 project under contract No.11227902 from the National Natural Science Foundation of China。
文摘Altermagnets represent a newly discovered class of magnetically ordered materials.Among all the candidates,CrSb stands out due to its largest spin splitting energy and highest Néel temperature exceeding 700 K,making it promising for room-temperature spintronic applications.Here we have successfully grown high quality CrSb(100)thin film on GaAs(110)substrate by molecular beam epitaxy.Using angle-resolved photoemission spectroscopy,we successfully obtained the three-dimensional electronic structure of the thin film.Moreover,we observed the emergence of the altermagnetic splitting bands corresponding to the calculated results along the low symmetry pathsT-QandP-D.The bands near the Fermi level are only spin splitting bands along theP-Ddirection,with splitting energy reaching as high as 910 meV.This finding provides insights into the magnetic properties of CrSb thin films and paves the way for further studies on their electronic structure and potential applications in spintronics.
基金the National Natural Science Foundation of China(Grant No.12004439)Hunan Province Postgraduate Research and Innovation Project(Grant No.CX20230229)the computational resources from the High Performance Computing Center of Central South University.
文摘Unconventional antiferromagnetism dubbed as altermagnetism was first discovered in rutile structured magnets,which is featured by spin splitting even without the spin–orbital coupling effect.This interesting phenomenon has been discovered in more altermagnetic materials.In this work,we explore two-dimensional altermagnetic materials by studying two series of two-dimensional magnets,including MF4 with M covering all 3d and 4d transition metal elements,as well as TS2 with T=V,Cr,Mn,Fe.Through the magnetic symmetry operation of RuF4 and MnS2,it is verified that breaking the time inversion is a necessary condition for spin splitting.Based on symmetry analysis and first-principles calculations,we find that the electronic bands and magnon dispersion experience alternating spin splitting along the same path.This work paves the way for exploring altermagnetism in two-dimensional materials.
基金supported by the National Natural Science Foundation of China (22225301, 22303092)the Anhui Provincial Natural Science Foundation (2308085QB51)+4 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB0450101)the Fundamental Research Funds for the Central Universities (WK9990000153)the Innovation Program for Quantum Science and Technology (2021ZD0303302)the Supercomputing Centers of both the University of Science and Technology of China (USTCSCC)the Chinese Academy of Sciences (SCCAS)。
文摘Two-dimensional planar pentagonal crystals,long pursued for their geometrically frustrated lattice configurations and emergent quantum phenomena,have remained challenging to realize due to the intrinsic incompatibility of regular pentagons with Euclidean tiling.Here,we unveil 37 dynamically stable binary planar pentagonal monolayers through high-throughput computational screening of 1470 stoichiometric candidates.These materials exhibit room-temperature magnetism,including ferromagnetic(Curie temperature(T_(C))up to 521 K),antiferromagnetic(Néel temperature(T_(N))up to 761 K),and altermagnetic(TN=984 K)ground states,alongside unprecedented electronic states:Dirac semimetals,Dirac half-metal,nodal-loop semimetal,nodal-loop half-metal,and altermagnetic semiconductors(Mn_(4)N_(2))with giant spin splitting(0.78 eV).The latter achieves pure spin-polarized transport windows(-0.04 to 0.36 eV)and strain-tunable valley splitting(18.2 meV under 4%uniaxial strain).Intrinsic type-Ⅱ multiferroicity emerges in Fe_(4)C_(2) and Mn_(4)C_(2),featuring in-plane electric polarization(1.4 and 1.6 pC/m),ferroelasticity(0.8%and 1.2%reversible strain),and reversal chirality.Topological band analysis identifies chiral edge states in Dirac semimetal pentagons,alongside a magnetic topological insulator with Chern number|C|=2 in Mo_(2)S_(4) and W_(2)Te_(4).Temperature-driven structural transitions in Os_(2)S_(4) and Tc_(2)S_(4) from pentagonal to Lieb lattices accompany topological state switching and metal-to-semiconductor transitions.This work establishes pentagonal lattices as a platform for symmetry-driven multifunctionality,bridging geometric frustration with applications in spintronics,nanoelectronics,and quantum devices.
基金supported by the National Key Research and Development Program of China(Grant Nos.2024YFA1611300,and 2023YFA1406500)the National Natural Science Foundation of China(Grant Nos.12474100,12204009,12204003,and 12174394)+4 种基金the Natural Science Foundation of Anhui Province(Grant No.2208085QA08)the HFIPS Director's Fund(Grant Nos.YZJJQY202304,and BJPY2023B05)the Anhui Provincial Major S&T Project(Grant No.s202305a12020005)the High Magnetic Field Laboratory of Anhui Province(Grant No.AHHMFX-2020-02)the Basic Research Program of the Chinese Academy of Sciences Based on Major Scientific Infrastructures(Grant No.JZHKYPT-2021-08)。
文摘Recently,the altermagnets,a new kind of collinear antiferromagnet with nearly zero net magnetization and momentumdependent spin-splitting of bands,have sparked great interest.Despite simple magnetic structures,these altermagnets exhibit intriguing and intricate dependence of anomalous Hall effect(AHE)on the Néel vector,in contrast to the conventional perpendicular configuration of Hall current with magnetization in ferromagnets.However,the fundamental relationship between the AHE and the Néel vector remains largely elusive.Here,we reveal all the unconventional anomalous Hall textures in the Néel vector space,dubbed anomalous-Hall Néel textures(AHNTs)for altermagnets.Specifically,we identify 10 types across four categories of AHNTs for all altermagnets.Notably,we find that AHNTs resemble the known spin textures in momentum space and further reveal their symmetry origin.Meanwhile,we examine our key discoveries in prototypical altermagnets.Our work offers a thorough understanding of AHE in altermagnets and a complete and pictorial classification of altermagnets based on the geometry of response functions.
基金supported by the National Natural Science Foundation of China(12474155,12447163,and 11904250)the Zhejiang Provincial Natural Science Foundation of China(LR25A040001)+1 种基金the China Postdoctoral Science Foundation(2025M773440)the U.S.DOE,Office of Science BES,Award No.DE-SC0004890(Y.L,I.Z.).
文摘Altermagnets,with spin splitting and vanishing magnetization,have been attributed to many fascinating phenomena and potential applications.In particular,integrating ferroelectricity with altermagnetism to enable magnetoelectric coupling and electric control of spin has drawn significant attention.However,its experimental realization and precise spin manipulation remain elusive.Here,by focusing on molecular ferroelectrics,the first discovered ferroelectrics renowned for their highly controllable molecular polarizations and structural flexibility,we reveal that these obstacles can be removed by an emergent multiferroic altermagnet with tunable spin polarization in a large class of fabricated organic materials.Using a symmetry-based design and a tight-binding model,we uncover the underlying mechanism of such molecular ferroelectric altermagnets and demonstrate how noncollinear molecular polarization can switch the spin polarization on and off and even reverse its sign,as detectable by the magneto-optical Kerr effect.From the first-principles calculations,we verify the feasibility of these materials in a series of well-established hybrid organic-inorganic perovskites and metal-organic frameworks.Our findings bridge molecular ferroelectrics and altermagnetic spintronics,highlighting an unexplored potential of multifunctional organic multiferroics.
文摘Altermagnets—recognized among the Science Breakthroughs of the Year 2024—have rapidly emerged as a new frontier,unifying the zero net magnetization of antiferromagnets with the spin polarization of ferromagnets[1-3].They are widely regarded as promising candidates for next-generation spintronics,yet the critical challenge of realizing precise,low-power electrical control of spin continues to draw intense attention[4-7].
基金supported by the Key Project of the Natural Science Program of Xinjiang Uygur Autonomous Region(Grant No.2023D01D03)the National Natural Science Foundation of China(Grant Nos.52073308,T2495212,and 12004439)+2 种基金the Tianchi-Talent Project for Young Doctors of Xinjiang Uygur Autonomous Region(Grant No.51052300570)the Outstanding Doctoral Student Innovation Project of Xinjiang University(Grant No.XJU2023BS028)carried out in part using computing resources at the High-Performance Computing Center of Central South University.
文摘Altermagnetic materials have recently attracted significant attention due to their unique intrinsic crystal symmetry.Breaking the lattice symmetry can yield a non-negligible piezomagnetic effect,which refers to a linear relationship between strain and magnetization.We proposed a method based onε_(xz)andε_(xy)shear strains that induced additional spin splitting along band paths that were originally spin-degenerate and generated weak ferromagnetic moments in altermagnetic CoF_(2)and RuO_(2).Additionally,the signs of spin splitting and weak ferromagnetic moments were switched by reversing the shear strain direction.The weak ferromagnetism had a substantial contribution from the orbital magnetic moments,with its y(z)component associated with the charge quadrupole moment.Our study highlights that shear strain provides a novel approach for exploring the physical properties of spin splitting,piezomagnetism,and multipolar order,while also broadening avenues for tuning the properties of altermagnetic materials.
文摘Spintronics exploits magnetic order parameters to encode binary information and utilizes spin-dependent transport for data processing[1].To date,most spintronic devices have been based on ferromagnetic materials,which offer straightforward information writing and reading through manipulation and detection of their magnetization.A prototypical device is the magnetic tunnel junction(MTJ),where non-volatile memory readout is achieved via the tunneling magnetoresistance(TMR)effect—distinct resistance states arising from parallel and antiparallel alignments of ferromagnetic electrodes.MTJs serve as the building blocks of magnetic random-access memories(MRAMs),which have already found commercial applications.
基金supported by the National Natural Science Foundation of China(Grant No.22073034)Junwei Liu was supported by the Hong Kong Research Grants Council(Grant Nos.16306220,16303821,16306722,and 16304523).
文摘According to recent studies on sliding/moire ferroelectricity,most 2D van der Waals nonferroelectric monolayers can become ferroelectric via multilayer stacking.In this paper,we propose that a similar strategy can be used to induce desirable van der Waals altermagnetism with symmetry-compensated collinear magnetic orders and non-relativistic spin splitting.Our first-principles calculations show the pervasive co-existence of sliding ferroelectricity and altermagnetism in a series of magnetic multilayers with antiparallel stacking configurations.Upon a twist angle in bilayers,moire ferroelectricity can be combined with altermagnetism,while some untwisted bilayers with zero net magnetizations exhibit non-relativistic spin splittings coupled with sliding ferroelectricity.Our study significantly expands the scope of altermagnetism,and its combination with sliding/moire ferroelectricity brings in new physics as well as promising applications,which should stimulate further experimental efforts.
基金the Shenzhen Natural Science Fund(the Stable Support Plan Program 20231121110218001)China Postdoctoral Science Foundation(2023M742403)for financial support.
文摘ABN_(3)-type nitride perovskites offer a rich platform for multifunctional materials but remain synthetically elusive.Here,we develop a machine learning(ML)-guided framework to expand the library of nitride perovskites and identify multiferroic candidates.By integrating positive-unlabeled(PU)learning with crystal graph convolutional neural networks(CGCNN),we screen 1465 ABN_(3)compositions and predict 96 synthesizable compounds.Further symmetry and magnetic filtering yield 4 altermagnetic ferroelectric(AM-FE)perovskites.Among them,CeCrN_(3)emerges as a promising candidate,exhibiting a bandgap of 0.30 eV,a spontaneous polarization of 0.59μC/cm^(2),a high Curie temperature of 650 K,and a low polarization switching barrier of 53 meV,as confirmed by density functional theory(DFT)calculations.In addition,CeCrN_(3)demonstrates a pronounced bulk photovoltaic effect(BPVE),with the shift current reaching 44μA/V^(2)and an injection current reaching 2.4×10^(9)A/V^(2),both of which reverse upon FE switching.These findings not only advance the understanding of nitride perovskites but also provides a validated ML-DFT framework to guide experimental efforts in realizing novel functional materials.
基金J.-F.Jia thanks the Ministry of Science and Technology of China(Grants No.2019YFA0308600,2020YFA0309000)NSFC(Grants No.92365302,No.22325203,No.92265105,92065201,No.12074247,No.12174252,No.12488101)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)the Science and Technology Commission of Shanghai Municipality(Grants No.2019SHZDZX01,No.19JC1412701,No.20QA1405100)for financial supportJ.-F.Jia thanks the financial support from Innovation program for Quantum Science and Technology(Grant No.2021ZD0302500).
文摘Altermagnetism emerges as the third fundamental collinear magnetism recently.Associating nontrivial topology and quantum orders to this newly established magnetism is an important physical topic and may lead to interesting physics such as unusual quantum spin Hall effect with time-reversal-symmetry breaking,topological superconductivity and spin-valley locking.Here,we first generalize the spinless Haldane model from the usual honeycomb lattice to the otherwise simpler square lattice.We then restore the doublet spin degree of freedom,the resulted spinful model resembles the Kane-Mele model and is able to describe the unprecedented physics which intertwine C-paired spin-valley locking,Dirac physics,nontrivial band topology and altermagnetism.Our works shed lights on future studies and applications in spintronics and valleytronics for altermagnetic materials,the lattice theories developed in this article may also find their broad applications to optical lattice with ultra cold atoms,photonic lattice,etc.other than the usual electronic systems.
基金supported by the National Natural Science Foundation of China(Grant Nos.U24A6002,12174237(X.X.),52471253(F.W.),12404091(J.L.),52171183(Z.Q.))the support from the National Key Research and Development Program of China(Grant No.2022YFB3505301)+4 种基金the support from the Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province(Grant No.20240019)Central Government’s Special Fund for Local Science and Technology Development(Grant No.YDZJSX2024D058)the support from the Basic Research Plan of Shanxi Province(Grant No.202403021212016)the support from the Fundamental Research Program of Shanxi Province(Grant No.202403021222252)the Higher Education Science and Technology Innovation Plan Project of Shanxi(Grant No.2024L146)。
文摘The growing demand for artificial intelligence and complex computing has underscored the urgent need for advanced data storage technologies.Spin-orbit torque(SOT)has emerged as a leading candidate for high-speed,high-density magnetic random-access memory due to its ultrafast switching speed and low power consumption.This review systematically explores the generation and switching mechanisms of electron-mediated torques(including both conventional SOTs and orbital torques)and magnon-mediated torques.We discuss key materials that enable these effects:heavy metals,topological insulators,low-crystal-symmetry materials,non-collinear antiferromagnets,and altermagnets for conventional SOTs;3d,4d,and 5d transition metals for orbital torques;and antiferromagnetic insulator Ni O-and multiferroic Bi Fe O_(3)-based sandwich structures for magnon torques.We emphasize that although key components of SOT devices have been demonstrated,numerous promising materials and critical questions regarding their underlying mechanisms remain to be explored.Therefore,this field represents a dynamic and rapidly evolving frontier in spintronics,offering significant potential for advancing next-generation information storage and computational technologies.
基金supported by the National Natural Science Foundation of China(Grant Nos.12204533,12434009,and 62476278)the National Key R&D Program of China(Grant No.2024YFA1408601)+1 种基金the Fundamental Research Funds for the Central Universitiesthe Research Funds of Renmin University of China(Grant No.24XNKJ15)。
文摘Unconventional magnetism,including altermagnetism and unconventional compensated magnetism,characterized by its duality of real-space antiferromagnetic alignment and momentum-space spin splitting,has garnered widespread attention.While altermagnetism has been extensively studied,research on unconventional compensated magnetism remains very rare.In particular,unconventional compensated magnetic materials are only theoretically predicted and have not yet been synthesized experimentally.In this study,based on symmetry analysis and frst-principles electronic structure calculations,we predict that LaMn_(2)SbO_(6)is an unconventional compensated magnetic semiconductor.Given that the Mn ions at opposite spin lattice cannot be connected by any symmetry,the spin splitting in LaMn_(2)SbO_(6)is isotropic.More importantly,LaMn_(2)SbO_(6)has already been synthesized experimentally,and its magnetic structure has been confrmed by neutron scattering experiments.Therefore,LaMn_(2)SbO_(6)serves as an excellent material platform for investigating the novel physical properties of unconventional compensated magnetic materials.
基金supported by theNationalNatural Science Foundation ofChina(No.12474172)the Taishan Scholar Program of Shandong Province(No.ts20190906).
文摘Manipulating the spin and valley degrees of freedom of electrons is crucial for next-generation information technologies.Altermagnets,as an emerging magnetic phase,provide a quantum platform with intrinsic spin-valley locking,enabling multi-state manipulation of both spin and valley.Here,we propose a Janus monolayer CaCoFeN_(2),achieved through in situ substitution of magnetic transition metal atoms in the two-dimensional(2D)altermagnet Ca(CoN)2[Phys.Rev.Lett.133,056401(2024)].Our first-principles calculations identify CaCoFeN_(2) as an anisotropic spin-plasmon ferrovalley semiconductor,with a large valley splitting of 273 meV solely through crystal symmetry breaking,without any involvement of spin-orbit coupling(SOC).Furthermore,its anisotropic electronic structures facilitate highly directional spin plasmon propagation.Carrier-type switching(n-type↔ptype)reverses the anisotropy along orthogonal axes,yielding open equi-frequency contours in n-type CaCoFeN_(2).The integration of spontaneous spin and valley polarization within a single material without SOC,offers new opportunities for advancements in spintronics and valleytronics.
