Realizing ferromagnetic semiconductors with high Curie temperature TC is still a challenge in spintronics.Recent experiments have reported two-dimensional(2D)room temperature ferromagnetic metals,such as monolayer Cr_...Realizing ferromagnetic semiconductors with high Curie temperature TC is still a challenge in spintronics.Recent experiments have reported two-dimensional(2D)room temperature ferromagnetic metals,such as monolayer Cr_(3)Te_(6).In this paper,through density functional theory(DFT)calculations,we propose a method to obtain 2D high TC ferromagnetic semiconductors through element replacement in these ferromagnetic metals.We predict that monolayer(Cr_(4/6),Mo_(2/6))_(3)Te_(6),created via element replacement in monolayer Cr_(3)Te_(6),is a room-temperature ferromagnetic semiconductor exhibiting a band gap of 0.34 eV and a TC of 384 K.Our analysis reveals that the metal-to-semiconductor transition stems from the synergistic interplay of Mo-induced lattice distortion,which resolves band overlap,and the electronic contributions of Mo dopants,which further drive the formation of a distinct band gap.The origin of the high TC is traced to strong superexchange coupling between magnetic ions,analyzed via the superexchange model with DFT and Wannier function calculations.Considering the fast developments in fabrication and manipulation of 2D materials,our theoretical results propose an approach to explore high-temperature ferromagnetic semiconductors derived from experimentally obtained 2D high-temperature ferromagnetic metals through element replacement.展开更多
The present study reports large room-temperature ferromagnetism in Co and Tb co-doped GaN films and further investigates the correlation between the doping concentration and the magnetic moment.X-ray photoelectron spe...The present study reports large room-temperature ferromagnetism in Co and Tb co-doped GaN films and further investigates the correlation between the doping concentration and the magnetic moment.X-ray photoelectron spectroscopy(XPS)and X-ray diffraction(XRD)measurements confirm that most of the dopants are incorporated into the GaN lattice.Photoluminescence(PL)and Raman spectra results reveal that post-annealing repaired most of lattice defects induced by ion implantation.The ZFC/FC curves show a blocked phase related to Co precipitates in Co single-doped GaN system and this phase is suppressed by the incorporation of Tb ions in the co-doped GaN systems.Although the magnetic properties were enhanced with the co-implantation of Co and Tb ions,the magnetic moment introduced by each ion slightly decreased with increasing Tb concentration.Density functional theory(DFT)calculations suggest that a high doping concentration of Tb atoms leads to the antiferromagnetic phase in the nearest position between Co and Tb ions.Appropriate co-doping with Co and Tb ions in GaN favors the development of enhanced ferromagnetism with no secondary phase.Our study not only offers valuable insights for understanding the magnetic characteristics of co-doped GaN,but also highlights the viability of developing room-temperature diluted magnetic semiconductors by appropriately co-doping TM and RE elements.展开更多
Two-dimensional(2 D)few-layerVSe_(2),V_(1-x)Fe_(x)Se_(2) nanosheets have been synthesized by a hightemperature organic solution-phase method. The thickness of VSe_(2) nanosheets can be tuned from 12 to 5 layers by dec...Two-dimensional(2 D)few-layerVSe_(2),V_(1-x)Fe_(x)Se_(2) nanosheets have been synthesized by a hightemperature organic solution-phase method. The thickness of VSe_(2) nanosheets can be tuned from 12 to 5 layers by decreasing the precursor concentrations. The few-layer VSe_(2) nanosheets show the room-temperature ferromagnetism. The coercivity and magnetization reach 0.024 T and 0.036 mA·m^(2)·g^(-1) at room temperature. The chargedensity wave behavior is also confirmed in VSe_(2) by the hysteresis loops and zero-field-cooling curve. V_(1-x)Fe_(x)Se_(2) nanosheets can be obtained by doping Fe(acac)3 in the reaction process. The room-temperature coercivity and magnetization of V_(0.8)Fe_(0.2)Se_(2) nanosheets are 5 times higher than those of the pure VSe_(2) nanosheets without destroying the structures. The enhancement of magnetization is due to the coupling interaction of 3 d orbits between V and Fe atoms. Higher Fe concentration is beneficial to improve the coercivity, which is attributed to the formation of the second phase Fe3 Se4. This simple chemical preparation method can be extended to prepare the other 2 D materials.展开更多
Cux（Cu2O）1-x（0.09 x 1.00） granular films with thickness about 280 nm have been fabricated by direct current reactive magnetron sputtering. The atomic ratio x can be controlled by the oxygen flow rate during Cux（C...Cux（Cu2O）1-x（0.09 x 1.00） granular films with thickness about 280 nm have been fabricated by direct current reactive magnetron sputtering. The atomic ratio x can be controlled by the oxygen flow rate during Cux（Cu2O）1-x deposition. Room-temperature ferromagnetism（FM） is found in all of the samples. The saturated magnetization increases at first and then decreases with the decrease of x. The photoluminescence spectra show that the magnetization is closely correlated with the Cu vacancies in the Cux（Cu2O）1-x granular films. Fundamentally, the FM could be understood by the Stoner model based on the charge transfer mechanism. These results may provide solid evidence and physical insights on the origin of FM in the Cu2O-based oxides diluted magnetic semiconductors, especially for systems without intentional magnetic atom doping.展开更多
Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane.By combining X-ray absorption near the edge struct...Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane.By combining X-ray absorption near the edge structure spectrum and positron annihilation lifetime spectroscopy,Ti^3＋-V O defect complexes（or clusters） have been identified in annealed crystals at a high vacuum.We elucidate that the unpaired 3d electrons in Ti^3＋ ions provide the observed room-temperature ferromagnetism.In addition,excess oxygen ions in the TiO2 lattice could induce a number of Ti vacancies which obviously increase magnetic moments.展开更多
Two-dimensional (2D) ferromagnetic semiconductors have been recognized as the most promising candidates for next-generation low-cost, high-performance and nano-scale spintronic applications such as spin field-effect t...Two-dimensional (2D) ferromagnetic semiconductors have been recognized as the most promising candidates for next-generation low-cost, high-performance and nano-scale spintronic applications such as spin field-effect transistors and quantum computation/communication. However, as one of the 125 important scientific issues raised by Science journal in 2005 that "is it possible to create magnetic semiconductors that work at room temperature?", how to achieve a feasible ferromagnetic semiconductor with high Curie temperature is still a long-standing challenge despite of tremendous efforts have been devoted in this field since 1960s. The recent discovery of 2D ferromagnetic semiconductors Cr2Ge2Te6 and CrI3 has evoked new research interests in 2D intrinsic ferromagnetic semiconductors. But the low Curie temperature (<45 K) of these materials is still badly hindering their industrial applications.展开更多
Nd-doped In_2O_3 nanowires were fabricated by an Au-catalyzed chemical vapor deposition method.Nd atoms were successfully doped into the In_2O_3 host lattice structure,as revealed by energy dispersive x-ray spectrosco...Nd-doped In_2O_3 nanowires were fabricated by an Au-catalyzed chemical vapor deposition method.Nd atoms were successfully doped into the In_2O_3 host lattice structure,as revealed by energy dispersive x-ray spectroscopy,x-ray photoelectron spectroscopy,Raman spectroscopy,and x-ray diffraction.Robust room temperature ferromagnetism was observed in Nd-doped In_2O_3 nanowires,which was attributed to the long-range-mediated magnetization among Nd^（3＋）-vacancy complexes through percolation-bound magnetic polarons.展开更多
The intricate correlation between multiple degrees of freedom and physical properties is a fascinating area in solid state chemistry and condensed matter physics.Here,we report a quantum-magnetic system BaNi_(2)V_(2)O...The intricate correlation between multiple degrees of freedom and physical properties is a fascinating area in solid state chemistry and condensed matter physics.Here,we report a quantum-magnetic system BaNi_(2)V_(2)O_(8)(BNVO),in which the spin correlation was modulated by unusual oxidation state,leading to different magnetic behavior.The BNVO was modified with topochemical reduction(TR)to yield TR-BNVO with partially reduced valance state of Ni^(+)in the two-dimensional NiO_(6)-honeycomb lattice.Accordingly,the antiferromagnetic order is suppressed by the introduction of locally interposed Ni^(+)and oxygen vacancies,resulting in a ferromagnetic ground state with the transition temperature up to 710 K.A positive magnetoresistance(7.5%)was observed in the TR-BNVO at 40 K under 7 T.These findings show that topological reduction is a powerful approach to engineer low-dimensional materials and accelerate the discovery of new quantum magnetism.展开更多
Zn0.90Ni0.10O nanoparticles have been synthesized by single-bath two-electrode electrodeposition at constant voltage. X-ray diffraction, UV vis and photoluminescence studies reveal that a single-phase polycrystalline ...Zn0.90Ni0.10O nanoparticles have been synthesized by single-bath two-electrode electrodeposition at constant voltage. X-ray diffraction, UV vis and photoluminescence studies reveal that a single-phase polycrystalline hcp wurtzite crystal structure of ZnO is evolved. The material consists of a large number of defects such as oxygen vacancy (Ov) and zinc interstitial (Zi). The magnetization study reveals that the sample exhibits room-temperature global ferromagnetism and the ferromagnetic ordering seems to be defect induced via bound magnetic polaron mechanism, and double exchange is also expected to have played role. Interesting optoelectronic properties have been found in the synthesized sample and the material seems to be a potential candidate to be used as a UV sensor. Such a transition metal doped ZnO based dilute magnetic semiconducting system exhibiting room-temperature ferromagnetism is likely to be first of its kind in the sense that such materials have not yet been reported to be synthesized by the simple method of electrodeposition to the best of our knowledge on the basis of ample literature review.展开更多
Two-dimensional(2D)layered ferromagnets offer exciting opportunities for studying magnetic phenomena and developing advanced spintronic devices.In this study,we experimentally present a 2D chromium indium telluride(Cr...Two-dimensional(2D)layered ferromagnets offer exciting opportunities for studying magnetic phenomena and developing advanced spintronic devices.In this study,we experimentally present a 2D chromium indium telluride(Cr_(6)In_(2)Te_(12),CIT)that exhibits robust room-temperature ferromagnetism and remarkable magnetic properties.CIT demonstrates a high Curie temperature of 320 K,record-high room-temperature saturation magnetization(~52.3 emu g^(-1)),and a strong magnetocaloric effect.In addition,CIT displays complex magnetocrystalline anisotropy with multiple easy axes and signatures of an abnormal phase transition,characterized by anisotropic anomalies in field-and temperature-dependent magnetization curves.CIT also shows anisotropic magnetic interactions and critical exponents consistent with a mean-field model.Moreover,few-layer CIT retains clear room-temperature ferromagnetism.These exceptional properties position CIT as a promising 2D high-TC ferromagnet for multidisciplinary applications,particularly in high-performance spintronic devices.展开更多
Room-temperature ferromagnetism in graphene is a crucial step toward the practical application of spintronic devices.While hydrogen adsorption on graphene has been shown to induce magnetic moments,the overall efficien...Room-temperature ferromagnetism in graphene is a crucial step toward the practical application of spintronic devices.While hydrogen adsorption on graphene has been shown to induce magnetic moments,the overall efficiency remains low due to the clustering of hydrogen atoms and weak magnetic coupling.This study demonstrates a highly effective vacancy-assisted hydrogenation method to synthesize hydrogenated graphene(HG)with robust room-temperature ferromagnetism.The introduction of vacancies inhibits hydrogen clustering,increases magnetic edge atoms,and enhances the coupling between magnetic moments.As a result,HG exhibits a Curie temperature of 540 K and a saturation magnetization of 0.69 emu/g at 300 K.Our findings provide a new approach for the efficient hydrogenation of graphene,paving the way for its applications in spintronic devices.展开更多
Identifying air-stable two-dimensional(2D)ferromagnetism with high Curie temperature(T_(c))is highly desirable for its potential applications in next-generation spintronics.However,most of the work reported so far mai...Identifying air-stable two-dimensional(2D)ferromagnetism with high Curie temperature(T_(c))is highly desirable for its potential applications in next-generation spintronics.However,most of the work reported so far mainly focuses on promoting one specific key factor of 2D ferromagnetism(T_(c)or air stability),rather than comprehensive promotion of both of them.Herein,ultrathin Cr_(1-x)Te crystals grown by chemical vapor deposition(CVD)show thickness-dependent T_(c)up to 285 K.The out-of-plane ferromagnetic order is well preserved down to atomically thin limit(2.0 nm),as evidenced by anomalous Hall effect observed in non-encapsulated samples.Besides,the CVD-grown Cr_(1-x)Te nanosheets present excellent ambient stability,with no apparent change in surface roughness or electrical transport properties after exposure to air for months.Our work provides an alternative platform for investigation of intrinsic 2D ferromagnetism and development of innovative spintronic devices.展开更多
Material functionalities strongly depend on the stoichiometry,crystal structure,and homogeneity.Here we demonstrate an approach of amorphous nonstoichiometric inhomogeneous oxides to realize tunable ferromagnetism and...Material functionalities strongly depend on the stoichiometry,crystal structure,and homogeneity.Here we demonstrate an approach of amorphous nonstoichiometric inhomogeneous oxides to realize tunable ferromagnetism and electrical transport at room temperature.In order to verify the origin of the ferromagnetism,we employed a series of structural,chemical,and electronic state characterizations.Combined with electron microscopy and transport measurements,synchrotron-based grazing incident wide angle X-ray scattering,soft X-ray absorption and circular dichroism clearly reveal that the roomtemperature ferromagnetism originates from the In0.23Co0.77O1-v,amorphous phase with a large tunable range of oxygen vacancies.The room-temperature ferromagnetism is tunable from a high saturation magnetization of 500 emu cm-3 to below 25 emu cm-3,with the evolving electrical resistivity from5×103μΩ cm to above 2.5×105 μΩ cm.Inhomogeneous nano-crystallization emerges with decreasing oxygen vacancies,driving the system towards non-ferromagnetism and insulating regime.Our work unfolds the novel functionalities of amorphous nonstoichiometric inhomogeneous oxides,which opens up new opportunities for developing spintronic materials with superior magnetic and transport properties.展开更多
Two-dimensional(2D)materials that combine ferromagnetic,semiconductor,and piezoelectric properties hold significant potential for both fundamental research and spin electronic devices.However,the majority of reported ...Two-dimensional(2D)materials that combine ferromagnetic,semiconductor,and piezoelectric properties hold significant potential for both fundamental research and spin electronic devices.However,the majority of reported 2D ferromagnetic-semiconductor-piezoelectric materials rely on d-electron systems,which limits their practical applications due to a Curie temperature lower than room temperature(RT).Here,we report a high-crystallinity carbon nitride(CCN)material based on sp-electrons using a chemical vapor deposition strategy.CCN exhibits a band gap of 1.8 eV and has been confirmed to possess substantial in-plane and out-of-plane piezoelectricity.Moreover,we acquired clear evidences of ferromagnetic behavior at room temperature.Extensive structural characterizations combined with theoretical calculations reveal that incorporating structural oxygen into the highly ordered heptazine structure causes partial substitution of nitrogen sites,which is primarily responsible for generating room-temperature ferromagnetism and piezoelectricity.As a result,the strain in wrinkles can effectively modulate the domain behavior and piezoelectric potential at room temperature.The addition of RT ferromagnetic-semiconductor-piezoelectric material based on sp-electrons to the family of two-dimensional materials opens up numerous possibilities for novel applications in fundamental research and spin electronic devices.展开更多
Two-dimensional(2D)magnetic semiconductors are crucial in spin-based information-processing technologies due to the combination of the strong 2D quantum effects,surface effects and the control of spin states.However,m...Two-dimensional(2D)magnetic semiconductors are crucial in spin-based information-processing technologies due to the combination of the strong 2D quantum effects,surface effects and the control of spin states.However,most experimental approaches for tuning 2D magnets achieve pure ferromagnetism at low temperature.Herein,a defect engineering strategy using supercritical CO2 is introduced to achieve nanostructure with abundant defects for 2D MoO3−x,and room-temperature ferromagnetism can be obtained and tuned by introduction of the Mo5+ion depending on the change of supercritical pressure.In defective regions,the presence of the pentacoordinated[Mo5+O5]centers can achieve ferromagnetic ordering resulting in room-temperature ferromagnetism.With increasing supercritical pressure,it is easier for the supercritical CO2 to break the Mo–O bonds,achieving enhancement of the ferromagnetic performance with desired Curie temperature(>380 K).The magnetic responses in the MoO3−x system provide a step closer to the expansion of spin electronics.展开更多
Ferromagnetism in moiréflat-band systems has been extensively studied in the first valence miniband of twisted MoTe_(2),while its controlled realization at higher moiréfillings remains largely unexplored,exc...Ferromagnetism in moiréflat-band systems has been extensively studied in the first valence miniband of twisted MoTe_(2),while its controlled realization at higher moiréfillings remains largely unexplored,except for very recent works reporting correlated magnetism near half filling of the second moiréband.Here,we investigate rhombohedral-stacked twisted MoTe_(2)/hBN/WSe_(2) heterostructures and uncover two distinct ferromagnetic(FM)regions:one centered near v_(h)≈3(half filling of the second moirévalence miniband)at zero displacement field,and a re-entrant FM phase that emerges for v_(h)>3 only under a finite out-of-plane electric field.These FM regions are separated by a narrow filling window with a strongly suppressed magnetic circular dichroism(MCD)response.Layer-sensitive exciton spectroscopy identifies that WSe_(2) is hole-doped in the re-entrant FM region,consistent with partial charge transfer from MoTe_(2) to WSe_(2).We propose that electric-field–induced layer repopulation stabilizes the re-entrant ferromagnetic phase by pinning the effective MoTe_(2) filling near v_(h)≈3 while adding carriers to the remote WSe_(2) layer.Our results demonstrate that remote-layer population control is an effective tuning knob for magnetic ordering in higher moiréminibands,extending the design space for correlated spin–valley phases in transition metal dichalcogenide heterostructures.展开更多
In this work,silicon-germanium(SiGe)thin films are epitaxially grown on Ge substrates by ultra-high vacuum chemical vapor deposition and then doped with Mn element by ion-implantation and subsequent rapid thermal anne...In this work,silicon-germanium(SiGe)thin films are epitaxially grown on Ge substrates by ultra-high vacuum chemical vapor deposition and then doped with Mn element by ion-implantation and subsequent rapid thermal annealing(RTA).The characterizations show that the epitaxial SiGe thin films are single-crystalline with uniform tensile strain and then become polycrystalline after the ion implantation and following RTA.The magnetization measurements indicate that the annealed thin films exhibit Mn concentration-dependent ferromagnetism up to 309 K and the X-ray magnetic circular dichroism characterizations reveal the spin and orbital magnetic moments from the substitutional Mn element.To minimize the influence of anomalous Hall effect,magneto-transport measurements at a high magnetic field up to 31 T at 300 K are performed to obtain the hole mobility,which reaches a record-high value of~1230 cm^(2)V^(-1)s^(-1),owing to the crystalline quality and tensile strain-induced energy band modulation of the samples.The first demonstration of Mn-doped SiGe thin films with roomtemperature ferromagnetism and high carrier mobility may pave the way for practical semiconductor spintronic applications.展开更多
Two-dimensional(2D)ferromagnetic crystals with fascinating optical and electrical properties are crucial for nanotechnology and have a wide variety of applications in spintronics.However,low Curie temperatures of most...Two-dimensional(2D)ferromagnetic crystals with fascinating optical and electrical properties are crucial for nanotechnology and have a wide variety of applications in spintronics.However,low Curie temperatures of most 2D ferromagnetic crystals seriously hinder their practical applications,thus searching for intrinsic roomtemperature 2D ferromagnetic crystals is of great importance for development of information technology.Fortunately,progresses have been achieved in the last few years.Here we review recent advances in the field of intrinsic room-temperature 2D ferromagnetic crystals and introduce their applications in spintronic devices based on van der Waals heterostructures.Finally,the remaining challenge and future perspective on the development direction of intrinsic room-temperature 2D ferromagnetic crystals for 2D spintronics and van der Waals spintronics are briefly summarized.展开更多
Bio-based organic room-temperature phosphorescence(RTP)materials have drawn considerable interest due to their potential to replace conventional petroleum-based RTP materials and attain comprehensive full life-cycle c...Bio-based organic room-temperature phosphorescence(RTP)materials have drawn considerable interest due to their potential to replace conventional petroleum-based RTP materials and attain comprehensive full life-cycle carbon reduction,a feat attributable to their renewable,biocompatible,and environmentally friendly characteristics.Bio-based organic RTP materials derived from natural biomass(e.g.,cellulose,lignin,chitosan)or biologically produced substances possess the capacity to spontaneously generate RTP or contribute to its generation.In this paper,the development lineage of bio-based RTP materials is introduced from the above two directions,including different systems,how to construct such systems,and the current progress.With strategies including hydrogen bonding networks,host—vip encapsulation,and polymeric matrices,it achieves RTP lifetimes up to seconds and full visible-band emission.It then explores the application scenarios that emerge from the natural advantages of these materials,including anti-counterfeiting and encryption,environmental monitoring,and bioimaging.Finally,it brieflydiscusses the potential challenges associated with bio-based RTP materials and envisions future development directions for them.While bio-based RTP materials rival petroleum-based counterparts in RTP efficiency,challenges persist:high production costs,poor environmental/thermal stability,and balancing degradability with durability.These sustainable alternatives offer biodegradability,renewability,and reduced lifecycle carbon emissions,utilizing agricultural byproducts(e.g.,corn stalks,shrimp shells)to enhance circular economies.展开更多
Room-temperature phosphorescence(RTP)materials exhibiting long emission lifetimes have gained increasing attention owing to their potential applications in encryption,anti-counterfeiting,and sensing.However,most polym...Room-temperature phosphorescence(RTP)materials exhibiting long emission lifetimes have gained increasing attention owing to their potential applications in encryption,anti-counterfeiting,and sensing.However,most polymers exhibit a short RTP lifetime(<1 s)because of their unstable triplet excitons.Herein,a new strategy of polymer chain stabilized phosphorescence(PCSP),which yields a new kind of RTP polymers with an ultralong lifetime and a sensitive oxygen response,has been reported.The rigid polymer chains of poly(methyl mathacrylate)(PMMA)immobilize the emitter molecules through multiple interactions between them,giving rise to efficient RTP.Meanwhile,the loosely-packed amorphous polymer chains allow oxygen to diffuse inside,endowing the doped polymers with oxygen sensitivity.Flexible and transparent polymer films exhibited an impressive ultralong RTP lifetime of 2.57 s at room temperature in vacuum,which was among the best performance of PMMA.Intriguingly,their RTP was rapidly quenched in the presence of oxygen.Furthermore,RTP microparticles with a diameter of 1.63μm were synthesized using in situ dispersion polymerization technique.Finally,oxygen sensors for quick,visual,and quantitative oxygen detection were developed based on the RTP microparticles through phosphorescence lifetime and image analysis.With distinctive advantages such as an ultralong lifetime,oxygen sensitivity,ease of fabrication,and cost-effectiveness,PCSP opens a new avenue to sensitive materials for oxygen detection.展开更多
基金supported by the National Key R&D Program of China(Grant No.2022YFA1405100)Chinese Academy of Sciences Project for Young Scientists in Basic Research(Grant No.YSBR-030)+3 种基金the Basic Research Program of the Chinese Academy of Sciences Based on Major Scientific Infrastructures(Grant No.JZHKYPT-2021-08)GS was supported in part by the Innovation Program for Quantum Science and Technology(Grant No.2024ZD03005)the National Natural Science Foundation of China(Grant No.12447101)Chinese Academy of Sciences.
文摘Realizing ferromagnetic semiconductors with high Curie temperature TC is still a challenge in spintronics.Recent experiments have reported two-dimensional(2D)room temperature ferromagnetic metals,such as monolayer Cr_(3)Te_(6).In this paper,through density functional theory(DFT)calculations,we propose a method to obtain 2D high TC ferromagnetic semiconductors through element replacement in these ferromagnetic metals.We predict that monolayer(Cr_(4/6),Mo_(2/6))_(3)Te_(6),created via element replacement in monolayer Cr_(3)Te_(6),is a room-temperature ferromagnetic semiconductor exhibiting a band gap of 0.34 eV and a TC of 384 K.Our analysis reveals that the metal-to-semiconductor transition stems from the synergistic interplay of Mo-induced lattice distortion,which resolves band overlap,and the electronic contributions of Mo dopants,which further drive the formation of a distinct band gap.The origin of the high TC is traced to strong superexchange coupling between magnetic ions,analyzed via the superexchange model with DFT and Wannier function calculations.Considering the fast developments in fabrication and manipulation of 2D materials,our theoretical results propose an approach to explore high-temperature ferromagnetic semiconductors derived from experimentally obtained 2D high-temperature ferromagnetic metals through element replacement.
基金financially supported by the National Natural Science Foundation of China(Nos.12275027,11875088,12205016,61474142 and 61974162)the Young Elite Scientists Sponsorship Program by CAST(No.2023QNRC001)the Fund of Innovation Center of Radiation Application(No.KFZC2021020801).
文摘The present study reports large room-temperature ferromagnetism in Co and Tb co-doped GaN films and further investigates the correlation between the doping concentration and the magnetic moment.X-ray photoelectron spectroscopy(XPS)and X-ray diffraction(XRD)measurements confirm that most of the dopants are incorporated into the GaN lattice.Photoluminescence(PL)and Raman spectra results reveal that post-annealing repaired most of lattice defects induced by ion implantation.The ZFC/FC curves show a blocked phase related to Co precipitates in Co single-doped GaN system and this phase is suppressed by the incorporation of Tb ions in the co-doped GaN systems.Although the magnetic properties were enhanced with the co-implantation of Co and Tb ions,the magnetic moment introduced by each ion slightly decreased with increasing Tb concentration.Density functional theory(DFT)calculations suggest that a high doping concentration of Tb atoms leads to the antiferromagnetic phase in the nearest position between Co and Tb ions.Appropriate co-doping with Co and Tb ions in GaN favors the development of enhanced ferromagnetism with no secondary phase.Our study not only offers valuable insights for understanding the magnetic characteristics of co-doped GaN,but also highlights the viability of developing room-temperature diluted magnetic semiconductors by appropriately co-doping TM and RE elements.
基金financially supported by the National Natural Science Foundation of China(Nos.51971122,51571135 and 51701106)the National Key R&D Program of China(No.2017YFB0405703)。
文摘Two-dimensional(2 D)few-layerVSe_(2),V_(1-x)Fe_(x)Se_(2) nanosheets have been synthesized by a hightemperature organic solution-phase method. The thickness of VSe_(2) nanosheets can be tuned from 12 to 5 layers by decreasing the precursor concentrations. The few-layer VSe_(2) nanosheets show the room-temperature ferromagnetism. The coercivity and magnetization reach 0.024 T and 0.036 mA·m^(2)·g^(-1) at room temperature. The chargedensity wave behavior is also confirmed in VSe_(2) by the hysteresis loops and zero-field-cooling curve. V_(1-x)Fe_(x)Se_(2) nanosheets can be obtained by doping Fe(acac)3 in the reaction process. The room-temperature coercivity and magnetization of V_(0.8)Fe_(0.2)Se_(2) nanosheets are 5 times higher than those of the pure VSe_(2) nanosheets without destroying the structures. The enhancement of magnetization is due to the coupling interaction of 3 d orbits between V and Fe atoms. Higher Fe concentration is beneficial to improve the coercivity, which is attributed to the formation of the second phase Fe3 Se4. This simple chemical preparation method can be extended to prepare the other 2 D materials.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11104148,51101088,and 51171082)the Tianjin Natural Science Foundation,China(Grant Nos.14JCZDJC37700 and 13JCQNJC02800)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20110031110034)the Fundamental Research Funds for the Central Universities,China
文摘Cux（Cu2O）1-x（0.09 x 1.00） granular films with thickness about 280 nm have been fabricated by direct current reactive magnetron sputtering. The atomic ratio x can be controlled by the oxygen flow rate during Cux（Cu2O）1-x deposition. Room-temperature ferromagnetism（FM） is found in all of the samples. The saturated magnetization increases at first and then decreases with the decrease of x. The photoluminescence spectra show that the magnetization is closely correlated with the Cu vacancies in the Cux（Cu2O）1-x granular films. Fundamentally, the FM could be understood by the Stoner model based on the charge transfer mechanism. These results may provide solid evidence and physical insights on the origin of FM in the Cu2O-based oxides diluted magnetic semiconductors, especially for systems without intentional magnetic atom doping.
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 61006066)the National Natural Science Foundation of China (Grant No. 11175191)
文摘Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane.By combining X-ray absorption near the edge structure spectrum and positron annihilation lifetime spectroscopy,Ti^3＋-V O defect complexes（or clusters） have been identified in annealed crystals at a high vacuum.We elucidate that the unpaired 3d electrons in Ti^3＋ ions provide the observed room-temperature ferromagnetism.In addition,excess oxygen ions in the TiO2 lattice could induce a number of Ti vacancies which obviously increase magnetic moments.
文摘Two-dimensional (2D) ferromagnetic semiconductors have been recognized as the most promising candidates for next-generation low-cost, high-performance and nano-scale spintronic applications such as spin field-effect transistors and quantum computation/communication. However, as one of the 125 important scientific issues raised by Science journal in 2005 that "is it possible to create magnetic semiconductors that work at room temperature?", how to achieve a feasible ferromagnetic semiconductor with high Curie temperature is still a long-standing challenge despite of tremendous efforts have been devoted in this field since 1960s. The recent discovery of 2D ferromagnetic semiconductors Cr2Ge2Te6 and CrI3 has evoked new research interests in 2D intrinsic ferromagnetic semiconductors. But the low Curie temperature (<45 K) of these materials is still badly hindering their industrial applications.
基金Project supported by the National Natural Science Foundation of China(Grant No.11274003)the Priority Academic Program Development of Jiangsu Higher Education Institutions,Chinathe Fundamental Research Funds for the Central Universities,China
文摘Nd-doped In_2O_3 nanowires were fabricated by an Au-catalyzed chemical vapor deposition method.Nd atoms were successfully doped into the In_2O_3 host lattice structure,as revealed by energy dispersive x-ray spectroscopy,x-ray photoelectron spectroscopy,Raman spectroscopy,and x-ray diffraction.Robust room temperature ferromagnetism was observed in Nd-doped In_2O_3 nanowires,which was attributed to the long-range-mediated magnetization among Nd^（3＋）-vacancy complexes through percolation-bound magnetic polarons.
基金financially supported by the National Natural Science Foundation of China(NSFC,Nos.21875287,22090041)the Guangdong Basic and Applied Basic Research Foundation(No.2022B1515120014)。
文摘The intricate correlation between multiple degrees of freedom and physical properties is a fascinating area in solid state chemistry and condensed matter physics.Here,we report a quantum-magnetic system BaNi_(2)V_(2)O_(8)(BNVO),in which the spin correlation was modulated by unusual oxidation state,leading to different magnetic behavior.The BNVO was modified with topochemical reduction(TR)to yield TR-BNVO with partially reduced valance state of Ni^(+)in the two-dimensional NiO_(6)-honeycomb lattice.Accordingly,the antiferromagnetic order is suppressed by the introduction of locally interposed Ni^(+)and oxygen vacancies,resulting in a ferromagnetic ground state with the transition temperature up to 710 K.A positive magnetoresistance(7.5%)was observed in the TR-BNVO at 40 K under 7 T.These findings show that topological reduction is a powerful approach to engineer low-dimensional materials and accelerate the discovery of new quantum magnetism.
基金Project supported by the UGC-DAE,Consortium for Scientific Research,Indore through its CRS project bearing No.CSR-IC/MSRSR-12/CRS-220/2017-18/1301.
文摘Zn0.90Ni0.10O nanoparticles have been synthesized by single-bath two-electrode electrodeposition at constant voltage. X-ray diffraction, UV vis and photoluminescence studies reveal that a single-phase polycrystalline hcp wurtzite crystal structure of ZnO is evolved. The material consists of a large number of defects such as oxygen vacancy (Ov) and zinc interstitial (Zi). The magnetization study reveals that the sample exhibits room-temperature global ferromagnetism and the ferromagnetic ordering seems to be defect induced via bound magnetic polaron mechanism, and double exchange is also expected to have played role. Interesting optoelectronic properties have been found in the synthesized sample and the material seems to be a potential candidate to be used as a UV sensor. Such a transition metal doped ZnO based dilute magnetic semiconducting system exhibiting room-temperature ferromagnetism is likely to be first of its kind in the sense that such materials have not yet been reported to be synthesized by the simple method of electrodeposition to the best of our knowledge on the basis of ample literature review.
基金supported by the National Key Research and Development Project(Grant No.2024YFA1408802)the Key Research and Development Program of Shaanxi(Grant No.2025GH-YBXM-050)+4 种基金the National Natural Science Foundation of China(Grant Nos.52202186,62304069,62025402,62090033,91964202,92064003,92264202,62293522,12104352,and 12204294)the China National Postdoctoral Programme for Innovative Talents(BX20230281)Major Program of Zhejiang Natural Science Foundation(Grant No.DT23F0402)Xidian University Specially Funded Project for Interdisciplinary Exploration(TZJH2024064,TZJH2024053)the China Postdoctoral Science Foundation(Certificate Number:2024M752520).
文摘Two-dimensional(2D)layered ferromagnets offer exciting opportunities for studying magnetic phenomena and developing advanced spintronic devices.In this study,we experimentally present a 2D chromium indium telluride(Cr_(6)In_(2)Te_(12),CIT)that exhibits robust room-temperature ferromagnetism and remarkable magnetic properties.CIT demonstrates a high Curie temperature of 320 K,record-high room-temperature saturation magnetization(~52.3 emu g^(-1)),and a strong magnetocaloric effect.In addition,CIT displays complex magnetocrystalline anisotropy with multiple easy axes and signatures of an abnormal phase transition,characterized by anisotropic anomalies in field-and temperature-dependent magnetization curves.CIT also shows anisotropic magnetic interactions and critical exponents consistent with a mean-field model.Moreover,few-layer CIT retains clear room-temperature ferromagnetism.These exceptional properties position CIT as a promising 2D high-TC ferromagnet for multidisciplinary applications,particularly in high-performance spintronic devices.
基金the National Natural Science Foundation of China(Grant Nos.12104352 and 12204294)the China National Postdoctoral Programme for Innovative Talents(No.BX20230281)+2 种基金the Natural Science Basic Research Program of Shaanxi(Program No.2023JC-XJ-01)Xidian University Specially Funded Project for Interdisciplinary Exploration(No.TZJH2024064)the China Postdoctoral Science Foundation(Certificate No.2024M752520).
文摘Room-temperature ferromagnetism in graphene is a crucial step toward the practical application of spintronic devices.While hydrogen adsorption on graphene has been shown to induce magnetic moments,the overall efficiency remains low due to the clustering of hydrogen atoms and weak magnetic coupling.This study demonstrates a highly effective vacancy-assisted hydrogenation method to synthesize hydrogenated graphene(HG)with robust room-temperature ferromagnetism.The introduction of vacancies inhibits hydrogen clustering,increases magnetic edge atoms,and enhances the coupling between magnetic moments.As a result,HG exhibits a Curie temperature of 540 K and a saturation magnetization of 0.69 emu/g at 300 K.Our findings provide a new approach for the efficient hydrogenation of graphene,paving the way for its applications in spintronic devices.
基金J.X.W.acknowledges financial support from the National Natural Science Foundation of China(No.92064005)Beijing National Laboratory for Molecular Sciences(No.BNLMS201914)+4 种基金thanks S.S.D.in Tianjin Key Laboratory of Molecular Optoelectronic Sciences for her instrumental assistance on PPMS(Dynacool-9T)H.T.Y.acknowledges the support from the National Natural Science Foundation of China(Nos.91750101,21733001,52072168,and 51861145201)the National Key Basic Research Program of China(No.2018YFA0306200)the Fundamental Research Funds for the Central Universities(Nos.021314380078,021314380104,and 021314380147)Jiangsu Key Laboratory of Artificial Functional Materials。
文摘Identifying air-stable two-dimensional(2D)ferromagnetism with high Curie temperature(T_(c))is highly desirable for its potential applications in next-generation spintronics.However,most of the work reported so far mainly focuses on promoting one specific key factor of 2D ferromagnetism(T_(c)or air stability),rather than comprehensive promotion of both of them.Herein,ultrathin Cr_(1-x)Te crystals grown by chemical vapor deposition(CVD)show thickness-dependent T_(c)up to 285 K.The out-of-plane ferromagnetic order is well preserved down to atomically thin limit(2.0 nm),as evidenced by anomalous Hall effect observed in non-encapsulated samples.Besides,the CVD-grown Cr_(1-x)Te nanosheets present excellent ambient stability,with no apparent change in surface roughness or electrical transport properties after exposure to air for months.Our work provides an alternative platform for investigation of intrinsic 2D ferromagnetism and development of innovative spintronic devices.
基金supported by the National Natural Science Foundation of China (11434006, 11774199, and 51871112)the National Basic Research Program of China (2015CB921502)+1 种基金the 111 Project B13029supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DEAC02-76SF00515。
文摘Material functionalities strongly depend on the stoichiometry,crystal structure,and homogeneity.Here we demonstrate an approach of amorphous nonstoichiometric inhomogeneous oxides to realize tunable ferromagnetism and electrical transport at room temperature.In order to verify the origin of the ferromagnetism,we employed a series of structural,chemical,and electronic state characterizations.Combined with electron microscopy and transport measurements,synchrotron-based grazing incident wide angle X-ray scattering,soft X-ray absorption and circular dichroism clearly reveal that the roomtemperature ferromagnetism originates from the In0.23Co0.77O1-v,amorphous phase with a large tunable range of oxygen vacancies.The room-temperature ferromagnetism is tunable from a high saturation magnetization of 500 emu cm-3 to below 25 emu cm-3,with the evolving electrical resistivity from5×103μΩ cm to above 2.5×105 μΩ cm.Inhomogeneous nano-crystallization emerges with decreasing oxygen vacancies,driving the system towards non-ferromagnetism and insulating regime.Our work unfolds the novel functionalities of amorphous nonstoichiometric inhomogeneous oxides,which opens up new opportunities for developing spintronic materials with superior magnetic and transport properties.
基金the National Key R&D Program of China(No.2022ZD0119002)the National Natural Science Foundation of China(Nos.62025402,62090033,91964202,92064003,92264202,62293522,12104352,and 12204294)+3 种基金the Major Program of Zhejiang Natural Science Foundation(No.DT23F0402)the Fundamental Research Funds for the Central Universities(Nos.QTZX23040 and QTZX23079)the China National Postdoctoral Programme for Innovative Talents(No.BX20230281)the Natural Science Basic Research Program of Shaanxi(No.2023JC-XJ-01).
文摘Two-dimensional(2D)materials that combine ferromagnetic,semiconductor,and piezoelectric properties hold significant potential for both fundamental research and spin electronic devices.However,the majority of reported 2D ferromagnetic-semiconductor-piezoelectric materials rely on d-electron systems,which limits their practical applications due to a Curie temperature lower than room temperature(RT).Here,we report a high-crystallinity carbon nitride(CCN)material based on sp-electrons using a chemical vapor deposition strategy.CCN exhibits a band gap of 1.8 eV and has been confirmed to possess substantial in-plane and out-of-plane piezoelectricity.Moreover,we acquired clear evidences of ferromagnetic behavior at room temperature.Extensive structural characterizations combined with theoretical calculations reveal that incorporating structural oxygen into the highly ordered heptazine structure causes partial substitution of nitrogen sites,which is primarily responsible for generating room-temperature ferromagnetism and piezoelectricity.As a result,the strain in wrinkles can effectively modulate the domain behavior and piezoelectric potential at room temperature.The addition of RT ferromagnetic-semiconductor-piezoelectric material based on sp-electrons to the family of two-dimensional materials opens up numerous possibilities for novel applications in fundamental research and spin electronic devices.
基金the National Natural Science Foundation of China(No.21773216,51173170)the Henan-Provincial and the China-National Natural Science United Foundation(Project No.U2004208).
文摘Two-dimensional(2D)magnetic semiconductors are crucial in spin-based information-processing technologies due to the combination of the strong 2D quantum effects,surface effects and the control of spin states.However,most experimental approaches for tuning 2D magnets achieve pure ferromagnetism at low temperature.Herein,a defect engineering strategy using supercritical CO2 is introduced to achieve nanostructure with abundant defects for 2D MoO3−x,and room-temperature ferromagnetism can be obtained and tuned by introduction of the Mo5+ion depending on the change of supercritical pressure.In defective regions,the presence of the pentacoordinated[Mo5+O5]centers can achieve ferromagnetic ordering resulting in room-temperature ferromagnetism.With increasing supercritical pressure,it is easier for the supercritical CO2 to break the Mo–O bonds,achieving enhancement of the ferromagnetic performance with desired Curie temperature(>380 K).The magnetic responses in the MoO3−x system provide a step closer to the expansion of spin electronics.
基金supported by the National Key R&D Program of China(Grant Nos.2021YFA1400100 and 2021YFA1401400)the National Natural Science Foundation of China(Grant Nos.12550403,12174250 and 12141404)+2 种基金the Shanghai Jiao Tong University 2030 Initiative Program B(Grant No.WH510207202)support from JSPS KAKENHI(Grant Nos.21H05233 and 23H02052)the World Premier International Research Center Initiative(WPI),MEXT,Japan。
文摘Ferromagnetism in moiréflat-band systems has been extensively studied in the first valence miniband of twisted MoTe_(2),while its controlled realization at higher moiréfillings remains largely unexplored,except for very recent works reporting correlated magnetism near half filling of the second moiréband.Here,we investigate rhombohedral-stacked twisted MoTe_(2)/hBN/WSe_(2) heterostructures and uncover two distinct ferromagnetic(FM)regions:one centered near v_(h)≈3(half filling of the second moirévalence miniband)at zero displacement field,and a re-entrant FM phase that emerges for v_(h)>3 only under a finite out-of-plane electric field.These FM regions are separated by a narrow filling window with a strongly suppressed magnetic circular dichroism(MCD)response.Layer-sensitive exciton spectroscopy identifies that WSe_(2) is hole-doped in the re-entrant FM region,consistent with partial charge transfer from MoTe_(2) to WSe_(2).We propose that electric-field–induced layer repopulation stabilizes the re-entrant ferromagnetic phase by pinning the effective MoTe_(2) filling near v_(h)≈3 while adding carriers to the remote WSe_(2) layer.Our results demonstrate that remote-layer population control is an effective tuning knob for magnetic ordering in higher moiréminibands,extending the design space for correlated spin–valley phases in transition metal dichalcogenide heterostructures.
基金supported by the National Key Research and Development Program of China(2017YFB0405702)the National Natural Science Foundation of China(52172272)。
文摘In this work,silicon-germanium(SiGe)thin films are epitaxially grown on Ge substrates by ultra-high vacuum chemical vapor deposition and then doped with Mn element by ion-implantation and subsequent rapid thermal annealing(RTA).The characterizations show that the epitaxial SiGe thin films are single-crystalline with uniform tensile strain and then become polycrystalline after the ion implantation and following RTA.The magnetization measurements indicate that the annealed thin films exhibit Mn concentration-dependent ferromagnetism up to 309 K and the X-ray magnetic circular dichroism characterizations reveal the spin and orbital magnetic moments from the substitutional Mn element.To minimize the influence of anomalous Hall effect,magneto-transport measurements at a high magnetic field up to 31 T at 300 K are performed to obtain the hole mobility,which reaches a record-high value of~1230 cm^(2)V^(-1)s^(-1),owing to the crystalline quality and tensile strain-induced energy band modulation of the samples.The first demonstration of Mn-doped SiGe thin films with roomtemperature ferromagnetism and high carrier mobility may pave the way for practical semiconductor spintronic applications.
基金the National Key Research and Development Program of China(Grant No.2022YFE0134600)the National Natural Science Foundation of China(Grant Nos.52272152,61674063,and 62074061)+1 种基金the Foundation of Shenzhen Science and Technology Innovation Committee(Grant Nos.JCYJ20210324142010030 and JCYJ20180504170444967)the Fellowship of China Postdoctoral Science Foundation(Grant No.2022M711234)。
文摘Two-dimensional(2D)ferromagnetic crystals with fascinating optical and electrical properties are crucial for nanotechnology and have a wide variety of applications in spintronics.However,low Curie temperatures of most 2D ferromagnetic crystals seriously hinder their practical applications,thus searching for intrinsic roomtemperature 2D ferromagnetic crystals is of great importance for development of information technology.Fortunately,progresses have been achieved in the last few years.Here we review recent advances in the field of intrinsic room-temperature 2D ferromagnetic crystals and introduce their applications in spintronic devices based on van der Waals heterostructures.Finally,the remaining challenge and future perspective on the development direction of intrinsic room-temperature 2D ferromagnetic crystals for 2D spintronics and van der Waals spintronics are briefly summarized.
基金financial support from the National Natural Science Foundation of China(22125803,T2488302,and 22020102006)Postdoctoral Fellowship Program of CPSF(GZB20240220)+2 种基金the Guangxi Department of Science and Technology(AA23062016)Natural Science Foundation of Shanghai(25ZR1402108)Fundamental Research Funds for the Central Universities.
文摘Bio-based organic room-temperature phosphorescence(RTP)materials have drawn considerable interest due to their potential to replace conventional petroleum-based RTP materials and attain comprehensive full life-cycle carbon reduction,a feat attributable to their renewable,biocompatible,and environmentally friendly characteristics.Bio-based organic RTP materials derived from natural biomass(e.g.,cellulose,lignin,chitosan)or biologically produced substances possess the capacity to spontaneously generate RTP or contribute to its generation.In this paper,the development lineage of bio-based RTP materials is introduced from the above two directions,including different systems,how to construct such systems,and the current progress.With strategies including hydrogen bonding networks,host—vip encapsulation,and polymeric matrices,it achieves RTP lifetimes up to seconds and full visible-band emission.It then explores the application scenarios that emerge from the natural advantages of these materials,including anti-counterfeiting and encryption,environmental monitoring,and bioimaging.Finally,it brieflydiscusses the potential challenges associated with bio-based RTP materials and envisions future development directions for them.While bio-based RTP materials rival petroleum-based counterparts in RTP efficiency,challenges persist:high production costs,poor environmental/thermal stability,and balancing degradability with durability.These sustainable alternatives offer biodegradability,renewability,and reduced lifecycle carbon emissions,utilizing agricultural byproducts(e.g.,corn stalks,shrimp shells)to enhance circular economies.
基金National Natural Science Foundation of China(No.22475241)Guangdong Basic and Applied Basic Research Foundation(Nos.2022A1515010826 and 2023A1515012696)the Fundamental Research Funds for the Central Universities(Nos.17lgjc03 and 18lgpy04).
文摘Room-temperature phosphorescence(RTP)materials exhibiting long emission lifetimes have gained increasing attention owing to their potential applications in encryption,anti-counterfeiting,and sensing.However,most polymers exhibit a short RTP lifetime(<1 s)because of their unstable triplet excitons.Herein,a new strategy of polymer chain stabilized phosphorescence(PCSP),which yields a new kind of RTP polymers with an ultralong lifetime and a sensitive oxygen response,has been reported.The rigid polymer chains of poly(methyl mathacrylate)(PMMA)immobilize the emitter molecules through multiple interactions between them,giving rise to efficient RTP.Meanwhile,the loosely-packed amorphous polymer chains allow oxygen to diffuse inside,endowing the doped polymers with oxygen sensitivity.Flexible and transparent polymer films exhibited an impressive ultralong RTP lifetime of 2.57 s at room temperature in vacuum,which was among the best performance of PMMA.Intriguingly,their RTP was rapidly quenched in the presence of oxygen.Furthermore,RTP microparticles with a diameter of 1.63μm were synthesized using in situ dispersion polymerization technique.Finally,oxygen sensors for quick,visual,and quantitative oxygen detection were developed based on the RTP microparticles through phosphorescence lifetime and image analysis.With distinctive advantages such as an ultralong lifetime,oxygen sensitivity,ease of fabrication,and cost-effectiveness,PCSP opens a new avenue to sensitive materials for oxygen detection.
