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Joel S Miller - One of the best experts on this subject based on the ideXlab platform.
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Weak Ferromagnetic Ordering of the Li+[TCNE]• − (TCNE = Tetracyanoethylene) Organic Magnet with an Interpenetrating Diamondoid Structure
2016Co-Authors: Christoph Boehme, Joel S MillerAbstract:ABSTRACT: Li[TCNE] (TCNE = tetracyanoethylene) magnetically orders as a weak ferromagnet (canted antiferromagnet) below 21.0 ± 0.1 K, as observed from the bifurcation of the field-cooled and zero-field-cooled Magnetizations, as well as Remnant Magnetization. The structure, determined ab initio from synchrotron X-ray powder diffraction data, consists of a planar μ4-[TCNE] bound to four tetrahedral Li+ ions. The structure consists of two interpenetrating diamondoid sublattices, with closest interlattice distances of 3.43 and 3.48 Å. At 5 K this magnetic state is characterized by a coercivity of ∼30 Oe, a Remnant Magnetization of 10 emu·Oe/mol, and a canting angle of 0.5°. Tetracyanoethylene (TCNE) plays an important role in thedevelopment of organic-based magnetic materials. Mag-netically ordered materials with Tc’s up to 127 °C occur in compounds in which the [TCNE]• − radical anion coordinates to paramagnetic transition metal ions. In all cases, the [TCNE]• − S = 1/2 spins couple with spins on high-spin transition metal ions.1−4 These materials can possess 0-, 1-, 2-, and 3-D extended structures with S = 1/2 [TCNE] •−, μ-[TCNE]•−, μ4-[TCNE] •−, and μ4-[TCNE] •−, respectively. Additionally, for alkali cations,5−7 [TCNE]• − dimerizes as diamagnetic π-[TCNE]2 2 − with exceptionally long (∼2.9 Å)8,9 two-electron, four-center (2e−/4c) C−C bonds.10 As part of our systematic exploration of the unusual bonding associated with the [TCNE]2 2 − dimer, we unexpectedly discovered a new structural motif and magnetic ordering as a weak ferromagnet for Li+[TCNE]−. The reaction of TCNE and LiI forms a dark green product,11 with IR νCN absorptions at 2280, 2221, 2177, and 2137 c
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weak ferromagnetic ordering of the li tcne tcne tetracyanoethylene organic magnet with an interpenetrating diamondoid structure
Journal of the American Chemical Society, 2013Co-Authors: Peter W Stephens, Royce A Davidson, Joshua D Bagnato, Kipp J Van Schooten, Christoph Boehme, Joel S MillerAbstract:Li[TCNE] (TCNE = tetracyanoethylene) magnetically orders as a weak ferromagnet (canted antiferromagnet) below 21.0 ± 0.1 K, as observed from the bifurcation of the field-cooled and zero-field-cooled Magnetizations, as well as Remnant Magnetization. The structure, determined ab initio from synchrotron X-ray powder diffraction data, consists of a planar μ4-[TCNE]•– bound to four tetrahedral Li+ ions. The structure consists of two interpenetrating diamondoid sublattices, with closest interlattice distances of 3.43 and 3.48 A. At 5 K this magnetic state is characterized by a coercivity of ∼30 Oe, a Remnant Magnetization of 10 emu·Oe/mol, and a canting angle of 0.5°.
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pressure induced transition from an antiferromagnet to a ferrimagnet for mn ii tcne c4 cn 8 1 2 tcne tetracyanoethylene
Inorganic Chemistry, 2012Co-Authors: Amber C Mcconnell, Joshua D Bell, Joel S MillerAbstract:MnII(TCNE)[C4(CN)8]1/2 (TCNE = tetracyanoethylene) exhibits a reversible pressure-induced piezomagnetic transition from a low Magnetization antiferromagnetic state to a high Magnetization ferrimagnetic state above 0.50 ± 0.15 kbar. In the ferrimagnetic state, the critical temperature, Tc, increases with increasing hydrostatic pressure and is ∼97 K at 12.6 kbar, the Magnetization increases by 3 orders of magnitude (1000-fold), and the material becomes a hard magnet with a significant Remnant Magnetization.
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magnetic ordering tc 90 k observed for layered feii tcne ncme 2 feiiicl4 tcne tetracyanoethylene
Journal of the American Chemical Society, 2006Co-Authors: Konstantin Pokhodnya, Peter W Stephens, Michael Bonner, Joel S MillerAbstract:[Fe(TCNE)(NCMe)2][FeCl4] is isolated from the reaction of TCNE and FeCl2(NCMe)2 and orders as a ferrimagnet below 90 K and is the initial member of a new class of magnets. It is the first metal−TCNE magnet with direct bonding between metal ion and [TCNE]•- whose structure has been determined, and it possesses a novel planar μ4-[TCNE]•- spin coupling unit bonded to four FeII's, with an axial pair of MeCNs. The [FeIIICl4]- anion occupies sites between the [FeII(TCNE•-)(NCMe)2]+ layers. [Fe(TCNE)(NCMe)2][FeCl4] has a coercive field of 1730 Oe and a Remnant Magnetization of 7500 emuK/mol at 50 K.
Hui Sun - One of the best experts on this subject based on the ideXlab platform.
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structural magnetic and dielectric properties in aurivillius phase srxbi6 xfe1 x 2co1 x 2ti3 xo18
Journal of The European Ceramic Society, 2019Co-Authors: Hui Sun, Xi Xie, Tiaoshu Yao, Yan Wang, Xiaobing ChenAbstract:Abstract SrxBi6-xFe1-x/2Co1-x/2Ti3+xO18 (x = 0, 0.25, 0.5, 0.75, 1)(SBFCT-x) ceramics were prepared by the sol-gel auto-combustion method, and their microstructures, ferroelectric, magnetic and dielectric properties were investigated. All samples show layer-perovskited Aurivillius phase, which confirms that Sr doping does not affect the structure of SBFCT ceramics. The coexistence of ferroelectricity and ferromagnetism were observed at room temperature for all the samples. The largest Remnant polarization (2Pr ˜ 17.4 μC/cm2) is observed in the SBFCT-1 ceramic, while the SBFCT-0.5 ceramic shows the highest Remnant Magnetization (2Mr ˜ 0.74 emu/g). To explore the effect of valance states of magnetic ions on the properties, we analysed the content variation of Fe2+, Co2+, and oxygen vacancies by the X-ray photoelectron spectroscopy results. Furthermore, dielectric anomalies have been found around 400 K, which can be ascribed to the hopping process of oxygen vacancies. The effects of Sr and Ti substitution on ferroelectric and magnetic properties have been investigated and discussed.
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electrical and magnetic properties of aurivillius phase bi5fe1 xnixti3o15 thin films prepared by chemical solution deposition
Journal of Alloys and Compounds, 2018Co-Authors: Hui Sun, Tianshu Yao, Hui Shen, Fengzhen Huang, Xiaobing ChenAbstract:Abstract The Aurivillius Bi5Fe1-xNixTi3O15 (BFNT-x) ( 0 ≤ x ≤ 0.5 ) thin films were deposited by chemical solution deposition route. The microstructures, electrical and magnetic properties were systematically investigated in BFNT films. It has been found that the c-orientation of the films increases with the increase of Ni content. The coexistence of weak ferromagnetism and ferroelectricity at room temperature were observed in BFNT films except the x = 0.5 sample. The BFNT-0.1 sample exhibits a maximum Remnant polarization 2Pr ∼49.3 μC/cm2, which is enhanced by 12.6% compared with that of the Ni-free thin film. The leakage current is decreased evidently with Ni content less than 0.3. The BFNT-0.1 film also shows the highest Remnant Magnetization 2Mr ∼2.14 emu/cm3. The origins of weak ferromagnetism in the BFNT films are attributed to the spin canting of the antiferromagnetic (AFM) coupling caused by Dzyaloshinskii-Moriya (DM) interaction based the Fe-O and Ni-O octahedral and affected by other causes as discussed. The saturation Magnetization values of in-plane loops are smaller than that of the out-of-plane loops, indicating obvious anisotropic magnetism. These results demonstrate that partial substitution of Ni for Fe is an effective way for improving the multiferroic properties of Aurivillius compounds.
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ferromagnetic ferroelectric properties and magneto dielectric effect of bi4 25la0 75fe0 5co0 5ti3o15 ceramics
Applied Physics Letters, 2013Co-Authors: Xiangyu Mao, Hui Sun, Wei Wang, Xiaobing ChenAbstract:Multiferroic properties of four-layered Bi4.25La0.75Fe0.5Co0.5Ti3O15 ceramics were carefully investigated. X-ray diffraction and high resolution transmission electron microscopy analyses indicate that the as-prepared sample is almost free from secondary phases, and Magnetization measurements confirm a ferromagnetic transition ∼483 K. At room temperature (RT), the sample shows a typical ferromagnetism with a Remnant Magnetization (2Mr) of ∼51.2 m emu/g, and a good ferroelectric hysteresis with a Remnant polarization (2Pr) of ∼15.4 μC/cm2. More importantly, an obvious magneto-dielectric (MD) effect has been found under a low magnetic field of 1 T at RT with a maximum of magneto-dielectric constant of ∼10.5%.
Xiaobing Chen - One of the best experts on this subject based on the ideXlab platform.
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structural magnetic and dielectric properties in aurivillius phase srxbi6 xfe1 x 2co1 x 2ti3 xo18
Journal of The European Ceramic Society, 2019Co-Authors: Hui Sun, Xi Xie, Tiaoshu Yao, Yan Wang, Xiaobing ChenAbstract:Abstract SrxBi6-xFe1-x/2Co1-x/2Ti3+xO18 (x = 0, 0.25, 0.5, 0.75, 1)(SBFCT-x) ceramics were prepared by the sol-gel auto-combustion method, and their microstructures, ferroelectric, magnetic and dielectric properties were investigated. All samples show layer-perovskited Aurivillius phase, which confirms that Sr doping does not affect the structure of SBFCT ceramics. The coexistence of ferroelectricity and ferromagnetism were observed at room temperature for all the samples. The largest Remnant polarization (2Pr ˜ 17.4 μC/cm2) is observed in the SBFCT-1 ceramic, while the SBFCT-0.5 ceramic shows the highest Remnant Magnetization (2Mr ˜ 0.74 emu/g). To explore the effect of valance states of magnetic ions on the properties, we analysed the content variation of Fe2+, Co2+, and oxygen vacancies by the X-ray photoelectron spectroscopy results. Furthermore, dielectric anomalies have been found around 400 K, which can be ascribed to the hopping process of oxygen vacancies. The effects of Sr and Ti substitution on ferroelectric and magnetic properties have been investigated and discussed.
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electrical and magnetic properties of aurivillius phase bi5fe1 xnixti3o15 thin films prepared by chemical solution deposition
Journal of Alloys and Compounds, 2018Co-Authors: Hui Sun, Tianshu Yao, Hui Shen, Fengzhen Huang, Xiaobing ChenAbstract:Abstract The Aurivillius Bi5Fe1-xNixTi3O15 (BFNT-x) ( 0 ≤ x ≤ 0.5 ) thin films were deposited by chemical solution deposition route. The microstructures, electrical and magnetic properties were systematically investigated in BFNT films. It has been found that the c-orientation of the films increases with the increase of Ni content. The coexistence of weak ferromagnetism and ferroelectricity at room temperature were observed in BFNT films except the x = 0.5 sample. The BFNT-0.1 sample exhibits a maximum Remnant polarization 2Pr ∼49.3 μC/cm2, which is enhanced by 12.6% compared with that of the Ni-free thin film. The leakage current is decreased evidently with Ni content less than 0.3. The BFNT-0.1 film also shows the highest Remnant Magnetization 2Mr ∼2.14 emu/cm3. The origins of weak ferromagnetism in the BFNT films are attributed to the spin canting of the antiferromagnetic (AFM) coupling caused by Dzyaloshinskii-Moriya (DM) interaction based the Fe-O and Ni-O octahedral and affected by other causes as discussed. The saturation Magnetization values of in-plane loops are smaller than that of the out-of-plane loops, indicating obvious anisotropic magnetism. These results demonstrate that partial substitution of Ni for Fe is an effective way for improving the multiferroic properties of Aurivillius compounds.
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ferromagnetic ferroelectric properties and magneto dielectric effect of bi4 25la0 75fe0 5co0 5ti3o15 ceramics
Applied Physics Letters, 2013Co-Authors: Xiangyu Mao, Hui Sun, Wei Wang, Xiaobing ChenAbstract:Multiferroic properties of four-layered Bi4.25La0.75Fe0.5Co0.5Ti3O15 ceramics were carefully investigated. X-ray diffraction and high resolution transmission electron microscopy analyses indicate that the as-prepared sample is almost free from secondary phases, and Magnetization measurements confirm a ferromagnetic transition ∼483 K. At room temperature (RT), the sample shows a typical ferromagnetism with a Remnant Magnetization (2Mr) of ∼51.2 m emu/g, and a good ferroelectric hysteresis with a Remnant polarization (2Pr) of ∼15.4 μC/cm2. More importantly, an obvious magneto-dielectric (MD) effect has been found under a low magnetic field of 1 T at RT with a maximum of magneto-dielectric constant of ∼10.5%.
Pawan Kumar - One of the best experts on this subject based on the ideXlab platform.
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effect of cobalt substitution on structural impedance ferroelectric and magnetic properties of multiferroic bi2fe4o9 ceramics
Ceramics International, 2016Co-Authors: S R Mohapatra, Pawan Kumar, B Sahu, M Chandrasekhar, S D Kaushik, S Rath, A K SinghAbstract:Abstract Structural, impedance, ferroelectric and magnetic properties were examined in multiferroic Bi2Fe4(1−x)Co4xO9 (0≤x≤0.02) ceramics synthesized via solid-state reaction method. X-ray diffraction analysis and Rietveld refinement showed secondary phase formation (for x≥0.01) which was subsequently confirmed from room temperature Raman spectroscopy study. The frequency dependence of impedance and electric modulus of the material showed the presence of non-Debye type relaxation in all the samples. The values of the activation energies calculated from imaginary impedance and modulus lay in the range of 0.92–0.99 eV which confirmed that the oxygen vacancies play an important role in the conduction mechanism. Moreover, suitable amount of Co substitution significantly enhanced the Remnant polarization (2Pr) from 0.1193 μC/cm2 (x=0) to 0.2776 μC/cm2 (x=0.02). Besides, room temperature M-H measurement showed improved ferromagnetic hysteresis loop for all the modified samples. The Remnant Magnetization (Mr) and coercive field (Hc) increased from 0.0007 emu/gm and 42 Oe for x=0–0.1401 emu/gm and 296 Oe for x=0.02. The improved ferroelectricity was due to Co 3d-O 2p hybridization and enhanced Magnetization originated from the partial substitution of Co3+ ions leading to breakdown of balance between the anti-parallel sub lattice Magnetization of Fe3+ ions.
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oxygen octahedra distortion induced structural and magnetic phase transitions in bi1 xcaxfe1 xmnxo3 ceramics
Journal of Applied Physics, 2015Co-Authors: Pawan Kumar, Nisha Shankhwar, A Srinivasan, Manoranjan KarAbstract:The co-doping of Ca and Mn in respective Bi and Fe-sites of BiFeO3 lattice leads to structural transition from rhombohedral (R3c space group) to orthorhombic (Pbnm space group) crystal symmetry. The tilt angle for anti-phase rotation of the oxygen octahedra of BiFeO3 at room temperature is observed to be ∼13.8°. It decreases with the increase in the co-doping percentage which suggests the composition-driven structural phase transition. The Remnant Magnetization for sample with 15% of co-doping becomes about 16 times that of BiFeO3. It may be attributed to the suppression of cycloid spin structure and uncompensated spins at the surface of nanocrystallites. Further increase in co-doping percentage results in the sharp reduction of Remnant Magnetization due to the dominant contribution from the collinear antiferromagnetic ordering in the Pbnm space group. The Arrott plot analysis clearly indicates the composition-driven crossover from the antiferromagnetic to weak ferromagnetic ordering and vice versa. Electron spin resonance results provide the evidence for the composition-driven phase transitions from an incommensurate spin cycloidal modulated state to one with nearly homogeneous spin order. The band gap (2.17 eV) of BiFeO3 measured using UV-Vis spectra was supported by the resonance Raman spectra.
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oxygen octahedra distortion induced structural and magnetic phase transitions in bi1 xcaxfe1 xmnxo3 ceramics
Journal of Applied Physics, 2015Co-Authors: Pawan Kumar, Nisha Shankhwar, A SrinivasanAbstract:The co-doping of Ca and Mn in respective Bi and Fe-sites of BiFeO3 lattice leads to structural transition from rhombohedral (R3c space group) to orthorhombic (Pbnm space group) crystal symmetry. The tilt angle for anti-phase rotation of the oxygen octahedra of BiFeO3 at room temperature is observed to be ∼13.8°. It decreases with the increase in the co-doping percentage which suggests the composition-driven structural phase transition. The Remnant Magnetization for sample with 15% of co-doping becomes about 16 times that of BiFeO3. It may be attributed to the suppression of cycloid spin structure and uncompensated spins at the surface of nanocrystallites. Further increase in co-doping percentage results in the sharp reduction of Remnant Magnetization due to the dominant contribution from the collinear antiferromagnetic ordering in the Pbnm space group. The Arrott plot analysis clearly indicates the composition-driven crossover from the antiferromagnetic to weak ferromagnetic ordering and vice versa. Elect...
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effect of structural transition on magnetic and dielectric properties of la and mn co substituted bifeo3 ceramics
Materials Chemistry and Physics, 2014Co-Authors: Pawan KumarAbstract:Abstract Bi 1− x La x Fe 1− x Mn x O 3 ( x = 0.000–0.300) ceramics prepared by the tartaric acid modified sol–gel technique have been studied to analyze the effect of composition driven structural transition on the magnetic properties of bismuth ferrite (BiFeO 3 ). It was found that the co-substitution of La & Mn at Bi & Fe sites leads to suppression of impurity phases (Bi 2 Fe 4 O 9 and Bi 25 FeO 40 ) which generally appear in BiFeO 3 . The quantitative crystallographic phase analysis has been carried out by double phase Rietveld analysis of all the XRD patterns which indicates the existence of compositional driven crystal structure transformation from rhombohederal (space group R3c ) to the orthorhombic (space group Pbnm ) with the increase in substitution concentration. The 5% co-substituted sample exhibit high Remnant Magnetization i.e. about 15 times that of BiFeO 3 which is due to the suppression of cycloid spin structure and enhanced canting angle of antiferromagnetically ordered spins caused by the crystal lattice distortion. However, further increase in substitution results in the reduction of Remnant Magnetization and coercivity due to the appearance of complete antiferromagnetic ordering in the orthorhombic structure because of the significant contribution from the crystallographic phase of Pbnm space group (as obtained from double phase Rietveld analysis). The frequency independent higher dielectric constant and lower dielectric loss were observed for 5% co-substitution. Hence, this particular composition may be interesting for device applications.
Dmitry Budker - One of the best experts on this subject based on the ideXlab platform.
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noncovalent force spectroscopy using wide field optical and diamond based magnetic imaging
Journal of Applied Physics, 2019Co-Authors: Sean Lourette, Lykourgos Bougas, Metin Kayci, Dmitry BudkerAbstract:A realization of the force-induced Remnant Magnetization spectroscopy technique of specific biomolecular binding is presented, where detection is accomplished with wide-field optical and diamond-based magnetometry using an ensemble of nitrogen-vacancy color centers. This diamond-based technique that has both optical and magnetic detection modalities may be adapted for massively parallel screening of arrays of nanoscale samples.A realization of the force-induced Remnant Magnetization spectroscopy technique of specific biomolecular binding is presented, where detection is accomplished with wide-field optical and diamond-based magnetometry using an ensemble of nitrogen-vacancy color centers. This diamond-based technique that has both optical and magnetic detection modalities may be adapted for massively parallel screening of arrays of nanoscale samples.
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noncovalent force spectroscopy using wide field optical and diamond based magnetic imaging
arXiv: Instrumentation and Detectors, 2019Co-Authors: Sean Lourette, Lykourgos Bougas, Metin Kayci, Dmitry BudkerAbstract:A realization of the force-induced Remnant Magnetization spectroscopy (FIRMS) technique of specific biomolecular binding is presented where detection is accomplished with wide-field optical and diamond-based magnetometry using an ensemble of nitrogen-vacancy (NV) color centers. The technique may be adapted for massively parallel screening of arrays of nanoscale samples.