Bi0.85La0.15FeO3 thin film was prepared on ATO glass substrates by sol-gel technique. The effect of La doping on phase structure, film surface quality, ion valence, and ferroelectric/magnetic properties of Bio.85La0.1...Bi0.85La0.15FeO3 thin film was prepared on ATO glass substrates by sol-gel technique. The effect of La doping on phase structure, film surface quality, ion valence, and ferroelectric/magnetic properties of Bio.85La0.15FeO3 film were investigated. La doping suppressed the formation of impurity phases and the transition of Fe3＋ to Fe2＋ ions at room temperature. Compared with the un-doped BiFeO3, La-doping also increased the average grain size and the film density, which resulted in the decrease of film leakage current density. The remanent polarization and saturation magnetization were enhanced significantly by La doping. The remanent polariza- tion of Bi0.85La0.15FeO3 films gradually decreased while saturation magnetization increased with the decrease of measuring tempera- ture within a range from 50 to 300 K.展开更多
In this perspective paper, we discuss possible ways to control magnetism using electric-field. Special focus is given to interface/surface magnetoelectric effects, which will become important when the thickness of mag...In this perspective paper, we discuss possible ways to control magnetism using electric-field. Special focus is given to interface/surface magnetoelectric effects, which will become important when the thickness of magnetic films drops to nanoscale. We show that significantly different mechanisms may lead to interface/surface magnetoelectric effects, providing great flexibility to apply such effects. As a result, we propose several protype devices utilizing these novel magnetoelectric effects, and strongly advocate experimental endeavors to realize such devices.展开更多
Hexagonal rare-earth manganites have attracted considerable interest due to their complex multiferroic properties,and they possess a spontaneous electric polarization and may be utilized in various technological appli...Hexagonal rare-earth manganites have attracted considerable interest due to their complex multiferroic properties,and they possess a spontaneous electric polarization and may be utilized in various technological applications ranging from solar cells to non-volatile memories and light polarizers.The narrow bandgap of hexagonal rare-earth manganite-based compounds can perform remarkable optical anisotropy properties,which make these very efficient photovoltaic materials in parallel with the widely used TiO_(2)-based materials.Substantial enlargement of the traditional field of hexagonal rare-earth manganite photocatalysis also arose in the last decade.This article imparts an extensive review of the rational synthesis,optical properties,structural characterization,and applications of hexagonal rare-earth manganite.Fundamental properties of hexagonal rare-earth perovskite manganite are also emphasized,and a range of unique applications in photocatalysis and photovoltaics are discussed.Eventually,we wind up this review with some linear perspectives and future research in this area.展开更多
The functionalities and diverse metastable phases of multiferroic BiFeO3(BFO)thin films depend on the misfit strain.Although mixed phase-induced strain relaxation in multiphase BFO thin films is well known,it is uncle...The functionalities and diverse metastable phases of multiferroic BiFeO3(BFO)thin films depend on the misfit strain.Although mixed phase-induced strain relaxation in multiphase BFO thin films is well known,it is unclear whether a singlecrystalline BFO thin film can accommodate misfit strain without the involvement of its polymorphs.Thus,understanding the strain relaxation behavior is key to elucidating the lattice strain–property relationship.In this study,a correlative strain analysis based on dark-field inline electron holography(DIH)and quantitative scanning transmission electron microscopy(STEM)was performed to reveal the structural mechanism for strain accommodation of a single-crystalline BFO thin film.The nanoscale DIH strain analysis results indicated a random combination of multiple strain states that acted as a primary strain relief,forming irregularly strained nanodomains.The STEM-based bond length measurement of the corresponding strained nanodomains revealed a unique strain accommodation behavior achieved by a statistical combination of multiple modes of distorted structures on the unit-cell scale.The globally integrated strain for each nanodomain was estimated to be close to1.5%,irrespective of the nanoscale strain states,which was consistent with the fully strained BFO film on the SrTiO3 substrate.Density functional theory calculations suggested that strain accommodation by the combination of metastable phases was energetically favored compared to single-phase-mediated relaxation.This discovery allows a comprehensive understanding of strain accommodation behavior in ferroelectric oxide films,such as BFO,with various low-symmetry polymorphs.展开更多
The magnetic and electronic properties of the geometrically frustrated triangular antiferromagnet CuCrO2 are investigated by first principles through density functional theory calculations within the generalized gradi...The magnetic and electronic properties of the geometrically frustrated triangular antiferromagnet CuCrO2 are investigated by first principles through density functional theory calculations within the generalized gradient approxi- mations （GGA）＋U scheme. The spin exchange interactions up to the third nearest neighbours in the ab plane as well as the coupling between adjacent layers are calculated to examine the magnetism and spin frustration. It is found that CuCrO2 has a natural two-dimensional characteristic of the magnetic interaction. Using Monte Carlo simulation, we obtain the Neel temperature to be 29.9 K, which accords well with the experimental value of 24 K. Based on non- collinear magnetic structure calculations, we verify that the incommensurate spiral-spin structure with （110） spiral plane is believable for the magnetic ground state, which is consistent with the experimental observations. Due to intra-layer geometric spin frustration, parallel helical-spin chains arise along the a, b, or a＋ b directions, each with a screw-rotation angle of about I20°. Our calculations of the density of states show that the spin frustration plays an important role in the change of d-p hybridization, while the spin-orbit coupling has a very limited influence on the electronic structure.展开更多
Multiferroic materials with two or more types of ferroic orders have attracted a great deal of atten- tion in the last decade for their magnetoelectric coupling, and new ideas and concepts have been ex- plored recentl...Multiferroic materials with two or more types of ferroic orders have attracted a great deal of atten- tion in the last decade for their magnetoelectric coupling, and new ideas and concepts have been ex- plored recently to develop multiferroic materials at nano-scale. Motivated by theoretical analysis, we synthesized single-phase BiFeO3 （BFO） nanofibers, Pb（Zr0.52Ti0.48）O3-CoFe2O4 （PZT-CFO） and Pb（Zro.52Tio.ns）Oa-NiFe204 （PZT-NFO） composite nanofibers, and CoFe2O4-Pb（Zr0.52Ti0.48）O3 （CFO-PZT） core-shell nanofibers using sol-gel based electrospinning. These nanofibers typically have diameters in the range of a few hundred nanometers and grain size in the range of 10s nanome- ters, and exhibits both ferroelectric and ferromagnetic properties. Piezoresponse force microscopy （PFM） based techniques have also been developed to examine the magnetoelectrie coupling of the nanofibers, which is estimated to be two orders of magnitude higher than that of thin films, con- sistent with our theoretical analysis. These nanofibers are promising for a variety of multiferroic applications.展开更多
The crystal structure,magnetic and electrical properties of Bi（0.96）Pb（0.04） FeO3 and Bi（0.92）Pb（0.04）RE（0.04）FeO3（RE=La,Sm,Dy and Yb）polycrystalline samples were prepared by the flash autocombustion techn...The crystal structure,magnetic and electrical properties of Bi（0.96）Pb（0.04） FeO3 and Bi（0.92）Pb（0.04）RE（0.04）FeO3（RE=La,Sm,Dy and Yb）polycrystalline samples were prepared by the flash autocombustion technique.X-ray diffraction（XRD）measurements show that the rare-earth doped compositions crystallized in rhombohedral symmetry of space group R3 c.The undoped sample consisted needle shape particles while rare earth substitution preferred platelet like particles as clarified from high resolution transmission electron microscopy（HRTEM）.Morphological features were examined using field emission scanning electron microscopy（FESEM）.Magnetization measurements showed that Yb^3＋ samples possessed the highest room temperature saturation magnetization while when Bi^3＋ ions were substituted by La^3＋ ions,a smaller MS（0.28 emu/g）was obtained.The coexistence of ferroelectric and magnetic transitions was detected using DSC and χM,indicating the multiferroic characteristics of Bi（0.92）Pb（0.04）RE（0.04）FeO3 crystallites.The Néel temperature shifted upwards with decreasing the ionic radius of rare earth ion.Nice correlation was established between microstructure,morphology and magnetic properties in view of the contribution of magnetocrystalline and shape anisotropy in the magnetic parameters values.展开更多
基金Project supported by National Natural Science Foundation of China(51072163,51001085)
文摘Bi0.85La0.15FeO3 thin film was prepared on ATO glass substrates by sol-gel technique. The effect of La doping on phase structure, film surface quality, ion valence, and ferroelectric/magnetic properties of Bio.85La0.15FeO3 film were investigated. La doping suppressed the formation of impurity phases and the transition of Fe3＋ to Fe2＋ ions at room temperature. Compared with the un-doped BiFeO3, La-doping also increased the average grain size and the film density, which resulted in the decrease of film leakage current density. The remanent polarization and saturation magnetization were enhanced significantly by La doping. The remanent polariza- tion of Bi0.85La0.15FeO3 films gradually decreased while saturation magnetization increased with the decrease of measuring tempera- ture within a range from 50 to 300 K.
文摘In this perspective paper, we discuss possible ways to control magnetism using electric-field. Special focus is given to interface/surface magnetoelectric effects, which will become important when the thickness of magnetic films drops to nanoscale. We show that significantly different mechanisms may lead to interface/surface magnetoelectric effects, providing great flexibility to apply such effects. As a result, we propose several protype devices utilizing these novel magnetoelectric effects, and strongly advocate experimental endeavors to realize such devices.
基金supported by National Key Research and Development Program of China(2021YFA1200700)The National Natural Science Foundation of China(No.52372120,T2222025 and 62174053)+1 种基金Shanghai Science and Technology Innovation Action Plan(21JC1402000 and 21520714100)the Fundamental Research Funds for the Central Universities。
基金Project supported by Science and Engineering Research Board (SERB),Department of Science and Technology (DST),Government of India(EMR/2016/007046)。
文摘Hexagonal rare-earth manganites have attracted considerable interest due to their complex multiferroic properties,and they possess a spontaneous electric polarization and may be utilized in various technological applications ranging from solar cells to non-volatile memories and light polarizers.The narrow bandgap of hexagonal rare-earth manganite-based compounds can perform remarkable optical anisotropy properties,which make these very efficient photovoltaic materials in parallel with the widely used TiO_(2)-based materials.Substantial enlargement of the traditional field of hexagonal rare-earth manganite photocatalysis also arose in the last decade.This article imparts an extensive review of the rational synthesis,optical properties,structural characterization,and applications of hexagonal rare-earth manganite.Fundamental properties of hexagonal rare-earth perovskite manganite are also emphasized,and a range of unique applications in photocatalysis and photovoltaics are discussed.Eventually,we wind up this review with some linear perspectives and future research in this area.
基金Samsung Research Fundings&Incubation Center of Samsung Electronics(Grant No.SRFCMA1702-01)Y.-M.K acknowledges partial support from the National Research Foundation of Korea(NRF)(Grant No.2023R1A2C2002403)funded by the Korean government in KoreaA.Borisevich acknowledges support from FaCT,an Energy Frontier Research Center funded by the U.S.Department of Energy,Office of Science,Office of Basic Energy Science,Collaboratives Research Division.
文摘The functionalities and diverse metastable phases of multiferroic BiFeO3(BFO)thin films depend on the misfit strain.Although mixed phase-induced strain relaxation in multiphase BFO thin films is well known,it is unclear whether a singlecrystalline BFO thin film can accommodate misfit strain without the involvement of its polymorphs.Thus,understanding the strain relaxation behavior is key to elucidating the lattice strain–property relationship.In this study,a correlative strain analysis based on dark-field inline electron holography(DIH)and quantitative scanning transmission electron microscopy(STEM)was performed to reveal the structural mechanism for strain accommodation of a single-crystalline BFO thin film.The nanoscale DIH strain analysis results indicated a random combination of multiple strain states that acted as a primary strain relief,forming irregularly strained nanodomains.The STEM-based bond length measurement of the corresponding strained nanodomains revealed a unique strain accommodation behavior achieved by a statistical combination of multiple modes of distorted structures on the unit-cell scale.The globally integrated strain for each nanodomain was estimated to be close to1.5%,irrespective of the nanoscale strain states,which was consistent with the fully strained BFO film on the SrTiO3 substrate.Density functional theory calculations suggested that strain accommodation by the combination of metastable phases was energetically favored compared to single-phase-mediated relaxation.This discovery allows a comprehensive understanding of strain accommodation behavior in ferroelectric oxide films,such as BFO,with various low-symmetry polymorphs.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10874021)
文摘The magnetic and electronic properties of the geometrically frustrated triangular antiferromagnet CuCrO2 are investigated by first principles through density functional theory calculations within the generalized gradient approxi- mations （GGA）＋U scheme. The spin exchange interactions up to the third nearest neighbours in the ab plane as well as the coupling between adjacent layers are calculated to examine the magnetism and spin frustration. It is found that CuCrO2 has a natural two-dimensional characteristic of the magnetic interaction. Using Monte Carlo simulation, we obtain the Neel temperature to be 29.9 K, which accords well with the experimental value of 24 K. Based on non- collinear magnetic structure calculations, we verify that the incommensurate spiral-spin structure with （110） spiral plane is believable for the magnetic ground state, which is consistent with the experimental observations. Due to intra-layer geometric spin frustration, parallel helical-spin chains arise along the a, b, or a＋ b directions, each with a screw-rotation angle of about I20°. Our calculations of the density of states show that the spin frustration plays an important role in the change of d-p hybridization, while the spin-orbit coupling has a very limited influence on the electronic structure.
文摘Multiferroic materials with two or more types of ferroic orders have attracted a great deal of atten- tion in the last decade for their magnetoelectric coupling, and new ideas and concepts have been ex- plored recently to develop multiferroic materials at nano-scale. Motivated by theoretical analysis, we synthesized single-phase BiFeO3 （BFO） nanofibers, Pb（Zr0.52Ti0.48）O3-CoFe2O4 （PZT-CFO） and Pb（Zro.52Tio.ns）Oa-NiFe204 （PZT-NFO） composite nanofibers, and CoFe2O4-Pb（Zr0.52Ti0.48）O3 （CFO-PZT） core-shell nanofibers using sol-gel based electrospinning. These nanofibers typically have diameters in the range of a few hundred nanometers and grain size in the range of 10s nanome- ters, and exhibits both ferroelectric and ferromagnetic properties. Piezoresponse force microscopy （PFM） based techniques have also been developed to examine the magnetoelectrie coupling of the nanofibers, which is estimated to be two orders of magnitude higher than that of thin films, con- sistent with our theoretical analysis. These nanofibers are promising for a variety of multiferroic applications.
文摘The crystal structure,magnetic and electrical properties of Bi（0.96）Pb（0.04） FeO3 and Bi（0.92）Pb（0.04）RE（0.04）FeO3（RE=La,Sm,Dy and Yb）polycrystalline samples were prepared by the flash autocombustion technique.X-ray diffraction（XRD）measurements show that the rare-earth doped compositions crystallized in rhombohedral symmetry of space group R3 c.The undoped sample consisted needle shape particles while rare earth substitution preferred platelet like particles as clarified from high resolution transmission electron microscopy（HRTEM）.Morphological features were examined using field emission scanning electron microscopy（FESEM）.Magnetization measurements showed that Yb^3＋ samples possessed the highest room temperature saturation magnetization while when Bi^3＋ ions were substituted by La^3＋ ions,a smaller MS（0.28 emu/g）was obtained.The coexistence of ferroelectric and magnetic transitions was detected using DSC and χM,indicating the multiferroic characteristics of Bi（0.92）Pb（0.04）RE（0.04）FeO3 crystallites.The Néel temperature shifted upwards with decreasing the ionic radius of rare earth ion.Nice correlation was established between microstructure,morphology and magnetic properties in view of the contribution of magnetocrystalline and shape anisotropy in the magnetic parameters values.
