Diluted ferromagnetic semiconductors(DMSs) that combine the properties of semiconductors with ferromagnetism have potential application in spin-sensitive electronic(spintronic) devices. The search for DMS material...Diluted ferromagnetic semiconductors(DMSs) that combine the properties of semiconductors with ferromagnetism have potential application in spin-sensitive electronic(spintronic) devices. The search for DMS materials exploded after the observation of ferromagnetic ordering in Ⅲ-Ⅴ(Ga,Mn)As films. Recently, a series of DMS compounds isostructural to iron-based superconductors have been reported. Among them, the highest Curie temperature TCo f 230 K has been achieved in(Ba,K)(Zn,Mn)2As2. However, most DMSs, including(Ga,Mn)As, are p-type, i.e., the carriers that mediate the ferromagnetism are holes. For practical applications, DMSs with n-type carriers are also advantageous. Very recently,a new DMS Ba(Zn,Co)2As2 with n-type carriers has been synthesized. Here we summarize the recent progress on this research stream. We will show that the homogeneous ferromagnetism in these bulk form DMSs has been confirmed by microscopic techniques, i.e., nuclear magnetic resonance(NMR) and muon spin rotation(μSR).展开更多
This paper proposes a universal spin-dependent variable range hopping theoretical model to describe various experimental transport phenomena observed in wide-band-gap oxide ferromagnetic semiconductors with high trans...This paper proposes a universal spin-dependent variable range hopping theoretical model to describe various experimental transport phenomena observed in wide-band-gap oxide ferromagnetic semiconductors with high transition metal concentration. The contributions of the 'hard gap' energy, Coulomb interaction, correlation energy, and exchange interaction to the electrical transport are considered in the universal variable range hopping theoretical model. By fitting the temperature and magnetic field dependence of the experimental sheet resistance to the theoretical model, the spin polarization ratio of electrical carriers near the Fermi level and interactions between electrical carriers can be obtained.展开更多
Ferromagnetic semiconductor Ga_(1–x)Mn_(x)As_(1–y)P_(y) thin films go through a metal–insulator transition at low temperature where electrical conduction becomes driven by hopping of charge carriers.In this regime,...Ferromagnetic semiconductor Ga_(1–x)Mn_(x)As_(1–y)P_(y) thin films go through a metal–insulator transition at low temperature where electrical conduction becomes driven by hopping of charge carriers.In this regime,we report a colossal negative magnetoresistance(CNMR)coexisting with a saturated magnetic moment,unlike in the traditional magnetic semiconductor Ga_(1–x)Mn_(x)As.By analyzing the temperature dependence of the resistivity at fixed magnetic field,we demonstrate that the CNMR can be consistently described by the field dependence of the localization length,which relates to a field dependent mobility edge.This dependence is likely due to the random environment of Mn atoms in Ga_(1-x)Mn_(x)As_(1-y)P_(y) which causes a random spatial distribution of the mobility that is suppressed by an increasing magnetic field.展开更多
The existence of intrinsic ferromagnetic semiconductors(FMSs)in twodimensional(2D)materials has been a long-term concern and pursuit.Recent breakthroughs in the 2D FMSs,such as CrGeTe3 and CrX3(X=Cl,Br,I)from bulk dow...The existence of intrinsic ferromagnetic semiconductors(FMSs)in twodimensional(2D)materials has been a long-term concern and pursuit.Recent breakthroughs in the 2D FMSs,such as CrGeTe3 and CrX3(X=Cl,Br,I)from bulk down to monolayer,have stimulated intensive researches on new physical phenomena and creative concepts.This minireview mainly summarizes recent progress of 2D intrinsic FMSs in theoretical side,and focuses on the ongoing strategies proposed to enhance ferromagnetism,involving the mechanisms of magnetic exchange interaction and the significance of magnetic anisotropy.Meanwhile,spin-related multifunctionality with ultrathin FMSs and their van de Waals heterostructures in magnetoelectric,valleytronic,and nondissipative electronic technology are introduced,as well as the current challenges and the prospects in this field are discussed.展开更多
By using first-principles electronic structure calculations,we propose a two-dimensional ferromagnetic semiconductor Li_(2)NiSe_(2)with a Curie temperature above 200 K.The structure of monolayer Li_(2)NiSe_(2)is dynam...By using first-principles electronic structure calculations,we propose a two-dimensional ferromagnetic semiconductor Li_(2)NiSe_(2)with a Curie temperature above 200 K.The structure of monolayer Li_(2)NiSe_(2)is dynamically stable,which is derived from the synthesized prototype compound Li_(2)Ni O_(2)and can be denoted as Li-decorated 1T-type NiSe_(2).The Ni–Se–Ni ferromagnetic superexchange dominates the magnetic couplings between the Ni atoms,which can be understood in the frame of the Goodenough–Kanamori–Anderson(GKA)rules.Our systematic study of monolayer Li_(2)NiSe_(2)enables its promising applications in spintronics and suggests a new choice to design two-dimensional ferromagnetic semiconductors.展开更多
The pressure effect on the crystalline structure of the I-II- V semiconductor Li(Zn,Mn)As ferromagnet is studied using in situ high-pressure x-ray diffraction and diamond anvil cell techniques. A phase transition st...The pressure effect on the crystalline structure of the I-II- V semiconductor Li(Zn,Mn)As ferromagnet is studied using in situ high-pressure x-ray diffraction and diamond anvil cell techniques. A phase transition starting at -11.6GPa is found. The space group of the high-pressure new phase is proposed as Pmca. Fitting with the Birch-Murnaghan equation of state, the bulk modulus B0 and its pressure derivative B0 of the ambient pressure structure with space group of F43m are B0 = 75.4 GPa and B0 = 4.3, respectively.展开更多
2x (FeNi/CoZnO)/ZnO/(CoZnO/Co) x2 spin-inJection devices were prepared by sputtering and photo-lithography. In the devices, two composite magnetic layers 2x(FeNi/CoZnO) and (CoZnO/Co)x2 with different coercivi...2x (FeNi/CoZnO)/ZnO/(CoZnO/Co) x2 spin-inJection devices were prepared by sputtering and photo-lithography. In the devices, two composite magnetic layers 2x(FeNi/CoZnO) and (CoZnO/Co)x2 with different coercivities were used to fabricate the ZnO-based semiconductor spin valve. Since the CoZnO ferromagnetic semiconductor layers touched the ZnO space layer directly, the significant spin injection from CoZnO into ZnO was observed by measuring the magnetoresistance of the spin-injection devices. The magnetoresistance reduced linearly with increasing temperature, from 1.12% at 90 K to 0.35% at room temperature.展开更多
[FeNi(3 nm)/Zn1-xCoxO(3 nm)]2/ZnO(d nm)/[Zn1-xCoxO(3 nm)/Co(3 nm)]2 (d=3 and 10) semiconductor junctions were prepared by magnetron sputtering system and photolithography. The spin valve effect was observe...[FeNi(3 nm)/Zn1-xCoxO(3 nm)]2/ZnO(d nm)/[Zn1-xCoxO(3 nm)/Co(3 nm)]2 (d=3 and 10) semiconductor junctions were prepared by magnetron sputtering system and photolithography. The spin valve effect was observed in these junctions because the utility of the ferromagnetic composite layers acted as soft and hard magnetic layers. The electrical detection was performed by measuring the magnetoresistance of these junctions to investigate the current spin polarization asc in the ZnO layer and the spin injection efficiency η of spin-polarized electrons. asc was reduced from 11.7% (and 10.5%) at 90 K to 7.31% (and 5.93%) at room temperature for d=3 (and d=10). And η was reduced from 39.5% (and 35.5%) at 90 K to 24.7% (and 20.0%) at room temperature for d=3 (and d=10).展开更多
This paper investigates the effect of Dresselhaus spin orbit coupling on the spin-transport properties of ferromagnet/insulator/semiconductor/insulator/ferromagnet double-barrier structures. The influence of the thick...This paper investigates the effect of Dresselhaus spin orbit coupling on the spin-transport properties of ferromagnet/insulator/semiconductor/insulator/ferromagnet double-barrier structures. The influence of the thickness of the insulator between the ferromagnet and the semiconductor on the polarization is also considered. The obtained results indicate that (i) the polarization can be enhanced by reducing the insulator layers at zero temperature, and (ii) the tunnelling magnetoresistance inversion can be illustrated by the influence of the Dresselhaus spin-orbit coupling effect in the double-barrier structure. Due to the Dresselhaus spin-orbit coupling effect, the tunnelling magnetoresistance inversion occurs when the energy of a localized state in the barrier matches the Fermi energy EF of the ferromagnetic electrodes.展开更多
Ge<sub>0.94</sub>Mn<sub>0.06</sub> nanocolumn thin film is a unique phase of GeMn diluted magnetic semiconductors (DMS) which exhibit Curie temperature (TC) > 400 K. The multilayers of Ge<...Ge<sub>0.94</sub>Mn<sub>0.06</sub> nanocolumn thin film is a unique phase of GeMn diluted magnetic semiconductors (DMS) which exhibit Curie temperature (TC) > 400 K. The multilayers of Ge<sub>0.94</sub>Mn<sub>0.06</sub> nanocolumns separated by nano-scaled spacers represent great interests for spintronic applications, such as spin valves or giant magneto-resistance (GMR) multilayers. In this article, we present the results obtained from the preliminary study on the exchange coupling in two types of GeMn nanocolumn/Ge multilayers. All the samples have been grown using molecular beam epitaxy (MBE). The superconducting quantum interference device (SQUID) magnetometer has been used to determine the magnetic properties of the samples. In the multilayer system Ge/[Ge<sub>0.94</sub>Mn<sub>0.06</sub>(40 nm)/Ge(d nm)]9/Ge<sub>0.94</sub>Mn<sub>0.06</sub>(40 nm)/Ge, no exchange coupling can be observed. Inversely, exchange coupling between the layers exists and depends on the thickness of the Ge spacers for the GeMn nanocolumns/Ge multilayer spin valve systems. The exchange coupling in the nanocolumns multilayer systems has been shown to be complex due to the leakage field induced by neighboring nanocolumns and the magnetic anisotropy of nanocolumns.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
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
The structural and magnetic properties of the Cu-doped ZnO(ZnO:Cu) under c-axis pressure were studied using first-principle calculations. It was found that the ZnO:Cu undergoes a structural transition from Wurtzit...The structural and magnetic properties of the Cu-doped ZnO(ZnO:Cu) under c-axis pressure were studied using first-principle calculations. It was found that the ZnO:Cu undergoes a structural transition from Wurtzite to Graphite-like structure at a c-axis pressure of 7–8 GPa. This is accompanied by an apparent loss of ferromagnetic stability, indicating a magnetic transformation from a ferromagnetic state to a paramagnetic-like state. Further studies revealed that the magnetic instability is closely related to the variation in crystalline field originated from the structural transition, which is in association with the overlapping of spin–charge density between the Cu^2+ and adjacent O^2-.展开更多
1 Results Inducing order in spin degree of freedomof charge carriers in conventional semiconductors and gettingroomtemperature ferromagnetism(RTFM) is an ongoing challenge in realizing spintronic devices .
Two-dimensional(2D)magnetic crystals have been extensively explored thanks to their potential applications in spintronics,valleytronics,and topological superconductivity.Here we report a novel monolayer magnet,namely ...Two-dimensional(2D)magnetic crystals have been extensively explored thanks to their potential applications in spintronics,valleytronics,and topological superconductivity.Here we report a novel monolayer magnet,namely puckered pentagonal VTe_(2)(PP-VTe_(2)),intriguing atomic and electronic structures of which were firmly validated from first-principles calculations.The PP-VTe_(2) exhibits strong intrinsic ferromagnetism and semiconducting property distinct from the half-metallic bulk pyrite VTe_(2)(BP-VTe_(2))phase.An unusual magnetic anisotropy with large magnetic exchange energies is found.More interestingly,the multiferroic coupling between its 2D ferroelasticity and in-plane magnetization is further identified in PP-VTe_(2),lending it unprecedented controllability with external strains and electric fields.Serving as an emergent 2D ferromagnetic semiconductor with a novel crystal structure,monolayer PP-VTe_(2) provides an ideal platform for exploring exotic crystalline and spin configurations in low-dimensional systems.展开更多
Carbon-based magnetic semiconductors are easy to be modified with low cost and low power consumption.While they can demonstrate robust long-range magnetic ordering and show great potential for application after introd...Carbon-based magnetic semiconductors are easy to be modified with low cost and low power consumption.While they can demonstrate robust long-range magnetic ordering and show great potential for application after introducing magnetic moments.Graphdiyne(GDY),as an allotrope of carbon,exhibits intrinsic semiconductor properties and paramagnetic properties due to its unique structure and the presence of sp carbon.To improve the magnetic properties of GDY and prepare excellent magnetic semiconductor materials,scientists have done a lot of related research work.The most direct and effective method to introduce magnetism is heteroatom doping.In this review,we have entirely described the latest GDY magnetism introduction methods,effects,and theoretical calculations,etc.Doping methods include post-doping and molecular design doping.The doping elements have covered non-metallic elements(N,H,F,Cl,S),metallic elements(Fe),and functional groups.The magnetic properties of the modified GDY materials were studied by experimental analysis and theoretical calculations.This review provides a sufficient basis and direction for related researches.展开更多
Fe/(Ga,Mn)As heterostructures were fabricated by all molecular-beam epitaxy.Double-crystal X-ray diffraction and high-resolution cross-sectional transmission electron micrographs show that the Fe layer has a well or...Fe/(Ga,Mn)As heterostructures were fabricated by all molecular-beam epitaxy.Double-crystal X-ray diffraction and high-resolution cross-sectional transmission electron micrographs show that the Fe layer has a well ordered crystal orientation and an abrupt interface.The different magnetic behavior between the Fe layer and(Ga, Mn)As layer is observed by superconducting quantum interference device magnetometry.X-ray photoelectron spectroscopy measurements indicate no Fe_2As and Fe-Ga-As compounds,i.e.,no dead magnetic layer at the interface, which strongly affects the magnetic proximity and the polarization of the Mn ion in a thin(Ga,Mn)As region near the interface of the Fe/(Ga,Mn)As heterostructure.展开更多
基金Project supported by the Chinese Ministry of Science and Technology(Grant No.2016YFA0300402)the National Natural Science Foundation of China(Grant No.11574265)+1 种基金the Natural Science Foundation of Zhejiang Province,China(Grant Nos.LR15A040001 and LY14A040007)the Fundamental Research Funds for the Central Universities,China
文摘Diluted ferromagnetic semiconductors(DMSs) that combine the properties of semiconductors with ferromagnetism have potential application in spin-sensitive electronic(spintronic) devices. The search for DMS materials exploded after the observation of ferromagnetic ordering in Ⅲ-Ⅴ(Ga,Mn)As films. Recently, a series of DMS compounds isostructural to iron-based superconductors have been reported. Among them, the highest Curie temperature TCo f 230 K has been achieved in(Ba,K)(Zn,Mn)2As2. However, most DMSs, including(Ga,Mn)As, are p-type, i.e., the carriers that mediate the ferromagnetism are holes. For practical applications, DMSs with n-type carriers are also advantageous. Very recently,a new DMS Ba(Zn,Co)2As2 with n-type carriers has been synthesized. Here we summarize the recent progress on this research stream. We will show that the homogeneous ferromagnetism in these bulk form DMSs has been confirmed by microscopic techniques, i.e., nuclear magnetic resonance(NMR) and muon spin rotation(μSR).
基金Project supported by the National Basic Research Program of China (Grant Nos. 2007CB924903 and 2009CB929202)the National Natural Science Foundation of China (Grant No. 10974120)
文摘This paper proposes a universal spin-dependent variable range hopping theoretical model to describe various experimental transport phenomena observed in wide-band-gap oxide ferromagnetic semiconductors with high transition metal concentration. The contributions of the 'hard gap' energy, Coulomb interaction, correlation energy, and exchange interaction to the electrical transport are considered in the universal variable range hopping theoretical model. By fitting the temperature and magnetic field dependence of the experimental sheet resistance to the theoretical model, the spin polarization ratio of electrical carriers near the Fermi level and interactions between electrical carriers can be obtained.
基金This work was supported by the National Science Foundation Grant No.DMR 1905277.
文摘Ferromagnetic semiconductor Ga_(1–x)Mn_(x)As_(1–y)P_(y) thin films go through a metal–insulator transition at low temperature where electrical conduction becomes driven by hopping of charge carriers.In this regime,we report a colossal negative magnetoresistance(CNMR)coexisting with a saturated magnetic moment,unlike in the traditional magnetic semiconductor Ga_(1–x)Mn_(x)As.By analyzing the temperature dependence of the resistivity at fixed magnetic field,we demonstrate that the CNMR can be consistently described by the field dependence of the localization length,which relates to a field dependent mobility edge.This dependence is likely due to the random environment of Mn atoms in Ga_(1-x)Mn_(x)As_(1-y)P_(y) which causes a random spatial distribution of the mobility that is suppressed by an increasing magnetic field.
基金Jiangsu 333 Project,Grant/Award Number:BRA2016353Natural Science Foundation of China,Grant/Award Numbers:21525311,21773027+1 种基金National Key Research and Development Program of China,Grant/Award Number:2017YFA0204800Scientific Research Foundation of Graduate School of Southeast University,Grant/Award Number:YBPY1969。
文摘The existence of intrinsic ferromagnetic semiconductors(FMSs)in twodimensional(2D)materials has been a long-term concern and pursuit.Recent breakthroughs in the 2D FMSs,such as CrGeTe3 and CrX3(X=Cl,Br,I)from bulk down to monolayer,have stimulated intensive researches on new physical phenomena and creative concepts.This minireview mainly summarizes recent progress of 2D intrinsic FMSs in theoretical side,and focuses on the ongoing strategies proposed to enhance ferromagnetism,involving the mechanisms of magnetic exchange interaction and the significance of magnetic anisotropy.Meanwhile,spin-related multifunctionality with ultrathin FMSs and their van de Waals heterostructures in magnetoelectric,valleytronic,and nondissipative electronic technology are introduced,as well as the current challenges and the prospects in this field are discussed.
基金the National Key Research and Development Program of China(Grant No.2019YFA0308603)the National Natural Science Foundation of China(Grant No.11934020).
文摘By using first-principles electronic structure calculations,we propose a two-dimensional ferromagnetic semiconductor Li_(2)NiSe_(2)with a Curie temperature above 200 K.The structure of monolayer Li_(2)NiSe_(2)is dynamically stable,which is derived from the synthesized prototype compound Li_(2)Ni O_(2)and can be denoted as Li-decorated 1T-type NiSe_(2).The Ni–Se–Ni ferromagnetic superexchange dominates the magnetic couplings between the Ni atoms,which can be understood in the frame of the Goodenough–Kanamori–Anderson(GKA)rules.Our systematic study of monolayer Li_(2)NiSe_(2)enables its promising applications in spintronics and suggests a new choice to design two-dimensional ferromagnetic semiconductors.
基金Supported by the National Natural Science Foundation and the Ministry of Science and Technology of Chinathe National Natural Science Foundation of China under Grant No U1530402+3 种基金the U.S. Department of Energy of Office of Science under Grant No DE-AC02-06CH11357the DOE-NNSA under Grant No DE-NA0001974the DOE-BES under Grant No DE-FG02-99ER45775the Instrumentation Funding of National Science Foundation
文摘The pressure effect on the crystalline structure of the I-II- V semiconductor Li(Zn,Mn)As ferromagnet is studied using in situ high-pressure x-ray diffraction and diamond anvil cell techniques. A phase transition starting at -11.6GPa is found. The space group of the high-pressure new phase is proposed as Pmca. Fitting with the Birch-Murnaghan equation of state, the bulk modulus B0 and its pressure derivative B0 of the ambient pressure structure with space group of F43m are B0 = 75.4 GPa and B0 = 4.3, respectively.
基金This work was supported by the National Natural Science Foundation of China under grant No. 50102019 and 50572053New Century Fund for Outstanding Scholars (Grant No. 040634).
文摘2x (FeNi/CoZnO)/ZnO/(CoZnO/Co) x2 spin-inJection devices were prepared by sputtering and photo-lithography. In the devices, two composite magnetic layers 2x(FeNi/CoZnO) and (CoZnO/Co)x2 with different coercivities were used to fabricate the ZnO-based semiconductor spin valve. Since the CoZnO ferromagnetic semiconductor layers touched the ZnO space layer directly, the significant spin injection from CoZnO into ZnO was observed by measuring the magnetoresistance of the spin-injection devices. The magnetoresistance reduced linearly with increasing temperature, from 1.12% at 90 K to 0.35% at room temperature.
基金supported by the State Key Project of Fundamental Research of China No.2007CB924903 and NSFC No.50572053
文摘[FeNi(3 nm)/Zn1-xCoxO(3 nm)]2/ZnO(d nm)/[Zn1-xCoxO(3 nm)/Co(3 nm)]2 (d=3 and 10) semiconductor junctions were prepared by magnetron sputtering system and photolithography. The spin valve effect was observed in these junctions because the utility of the ferromagnetic composite layers acted as soft and hard magnetic layers. The electrical detection was performed by measuring the magnetoresistance of these junctions to investigate the current spin polarization asc in the ZnO layer and the spin injection efficiency η of spin-polarized electrons. asc was reduced from 11.7% (and 10.5%) at 90 K to 7.31% (and 5.93%) at room temperature for d=3 (and d=10). And η was reduced from 39.5% (and 35.5%) at 90 K to 24.7% (and 20.0%) at room temperature for d=3 (and d=10).
基金supported by the National Natural Science Foundation of China (Grant No 10674040)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No 20060094002)
文摘This paper investigates the effect of Dresselhaus spin orbit coupling on the spin-transport properties of ferromagnet/insulator/semiconductor/insulator/ferromagnet double-barrier structures. The influence of the thickness of the insulator between the ferromagnet and the semiconductor on the polarization is also considered. The obtained results indicate that (i) the polarization can be enhanced by reducing the insulator layers at zero temperature, and (ii) the tunnelling magnetoresistance inversion can be illustrated by the influence of the Dresselhaus spin-orbit coupling effect in the double-barrier structure. Due to the Dresselhaus spin-orbit coupling effect, the tunnelling magnetoresistance inversion occurs when the energy of a localized state in the barrier matches the Fermi energy EF of the ferromagnetic electrodes.
文摘Ge<sub>0.94</sub>Mn<sub>0.06</sub> nanocolumn thin film is a unique phase of GeMn diluted magnetic semiconductors (DMS) which exhibit Curie temperature (TC) > 400 K. The multilayers of Ge<sub>0.94</sub>Mn<sub>0.06</sub> nanocolumns separated by nano-scaled spacers represent great interests for spintronic applications, such as spin valves or giant magneto-resistance (GMR) multilayers. In this article, we present the results obtained from the preliminary study on the exchange coupling in two types of GeMn nanocolumn/Ge multilayers. All the samples have been grown using molecular beam epitaxy (MBE). The superconducting quantum interference device (SQUID) magnetometer has been used to determine the magnetic properties of the samples. In the multilayer system Ge/[Ge<sub>0.94</sub>Mn<sub>0.06</sub>(40 nm)/Ge(d nm)]9/Ge<sub>0.94</sub>Mn<sub>0.06</sub>(40 nm)/Ge, no exchange coupling can be observed. Inversely, exchange coupling between the layers exists and depends on the thickness of the Ge spacers for the GeMn nanocolumns/Ge multilayer spin valve systems. The exchange coupling in the nanocolumns multilayer systems has been shown to be complex due to the leakage field induced by neighboring nanocolumns and the magnetic anisotropy of nanocolumns.
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supported by the National Natural Science Foundation of China(Grant Nos.51031004 and 51272078)the Natural Science Foundation of Guangdong,China(Grant No.S2012010008124)+3 种基金the National Basic Research Program of China(Grant No.2015CB921202)the Project for Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme(2014)International Science & Technology Cooperation Platform Program of Guangzhou,China(Grant No.2014J4500016)the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(Grant No.IRT1243)
文摘The structural and magnetic properties of the Cu-doped ZnO(ZnO:Cu) under c-axis pressure were studied using first-principle calculations. It was found that the ZnO:Cu undergoes a structural transition from Wurtzite to Graphite-like structure at a c-axis pressure of 7–8 GPa. This is accompanied by an apparent loss of ferromagnetic stability, indicating a magnetic transformation from a ferromagnetic state to a paramagnetic-like state. Further studies revealed that the magnetic instability is closely related to the variation in crystalline field originated from the structural transition, which is in association with the overlapping of spin–charge density between the Cu^2+ and adjacent O^2-.
文摘1 Results Inducing order in spin degree of freedomof charge carriers in conventional semiconductors and gettingroomtemperature ferromagnetism(RTFM) is an ongoing challenge in realizing spintronic devices .
基金supported by the National Key Research and Development Program of China(Nos.2020YFA0308800,2016YFA0202300,and 2016YFA0300902)the National Natural Science Foundation of China(Nos.91850120 and 11974045)the Strategic Priority Research Program(B)of CAS(No.XDB30000000)。
文摘Two-dimensional(2D)magnetic crystals have been extensively explored thanks to their potential applications in spintronics,valleytronics,and topological superconductivity.Here we report a novel monolayer magnet,namely puckered pentagonal VTe_(2)(PP-VTe_(2)),intriguing atomic and electronic structures of which were firmly validated from first-principles calculations.The PP-VTe_(2) exhibits strong intrinsic ferromagnetism and semiconducting property distinct from the half-metallic bulk pyrite VTe_(2)(BP-VTe_(2))phase.An unusual magnetic anisotropy with large magnetic exchange energies is found.More interestingly,the multiferroic coupling between its 2D ferroelasticity and in-plane magnetization is further identified in PP-VTe_(2),lending it unprecedented controllability with external strains and electric fields.Serving as an emergent 2D ferromagnetic semiconductor with a novel crystal structure,monolayer PP-VTe_(2) provides an ideal platform for exploring exotic crystalline and spin configurations in low-dimensional systems.
基金This work was supported by the the National Natural Science Foundation of China(Nos.51802324,51822208,21771187,21790050,21790051)the Frontier Science Research Project of the Chinese Academy of Sciences(No.QYZDB-SSW-JSC052)+1 种基金the Taishan Scholars Program of Shandong Province,China(No.tsqn201812111)the Research Project of Qingdao Institute of Bioenergy and Bioprocess Technology,Chinese Academy of Sciences(Nos.QIBEBT ZZBS 201809,SEI I202120).
文摘Carbon-based magnetic semiconductors are easy to be modified with low cost and low power consumption.While they can demonstrate robust long-range magnetic ordering and show great potential for application after introducing magnetic moments.Graphdiyne(GDY),as an allotrope of carbon,exhibits intrinsic semiconductor properties and paramagnetic properties due to its unique structure and the presence of sp carbon.To improve the magnetic properties of GDY and prepare excellent magnetic semiconductor materials,scientists have done a lot of related research work.The most direct and effective method to introduce magnetism is heteroatom doping.In this review,we have entirely described the latest GDY magnetism introduction methods,effects,and theoretical calculations,etc.Doping methods include post-doping and molecular design doping.The doping elements have covered non-metallic elements(N,H,F,Cl,S),metallic elements(Fe),and functional groups.The magnetic properties of the modified GDY materials were studied by experimental analysis and theoretical calculations.This review provides a sufficient basis and direction for related researches.
基金supported by the National Natural Science Foundation of China(Nos.61076117,60836002)the Fundamental Research Funds for the Central Universities(No.11ML33)
文摘Fe/(Ga,Mn)As heterostructures were fabricated by all molecular-beam epitaxy.Double-crystal X-ray diffraction and high-resolution cross-sectional transmission electron micrographs show that the Fe layer has a well ordered crystal orientation and an abrupt interface.The different magnetic behavior between the Fe layer and(Ga, Mn)As layer is observed by superconducting quantum interference device magnetometry.X-ray photoelectron spectroscopy measurements indicate no Fe_2As and Fe-Ga-As compounds,i.e.,no dead magnetic layer at the interface, which strongly affects the magnetic proximity and the polarization of the Mn ion in a thin(Ga,Mn)As region near the interface of the Fe/(Ga,Mn)As heterostructure.