L. Q. Chen

Technical Institute of Physics and Chemistry, Peping, Beijing, China

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Publications (230)842 Total impact

  • J.-M. Hu · Tianxiang Nan · Nian X. Sun · L.-Q. Chen ·
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    ABSTRACT: Multiferroic magnetoelectric nanostructures with coupled magnetization and electric polarization across their interfaces have stimulated intense research activities over the past decade. Such interface-based magnetoelectric coupling can be exploited to significantly improve the performance of many devices such as memories, tunable radio-frequency/microwave devices, and magnetic sensors. In this article, we introduce a number of current or developing technologies and discuss their limitations. We describe how the use of magnetoelectric nanostructures can overcome these limitations to optimize device performance. We also present challenges that need to be addressed in pursuing practical applications of magnetoelectric devices.
    MRS Bulletin 09/2015; 40(9):728-735. DOI:10.1557/mrs.2015.195 · 5.67 Impact Factor
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    ABSTRACT: We employ phase-field modeling to explore the elastic properties of artificially created 1-D domain walls in (001)p-oriented BiFeO3 thin films, composed of a junction of the four polarization variants, all with the same out-of-plane polarization. It was found that these junctions exhibit peculiarly high electroelastic fields induced by the neighboring ferroelastic/ferroelectric domains. The vortex core exhibits a volume expansion, while the anti-vortex core is more compressive. Possible ways to control the electroelastic field, such as varying material constant and applying transverse electric field, are also discussed.
    Applied Physics Letters 08/2015; 107(5). DOI:10.1063/1.4927750 · 3.30 Impact Factor
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    ABSTRACT: The properties of flowerlike microspheres ceria based nickel catalyst for low temperature methane steam reforming (SMR) were studied. The ceria microspheres were prepared by hydrothermal method. Catalyst of nano-sized nickel oxide particles based on flowerlike cerium oxide microspheres with high dispersion were prepared to achieve simultaneous dehydrogenation of methane and water molecules on multi-active sites. The catalyst was characterized by means of Scanning Electron Microscope (SEM) and X-ray diffraction (XRD). Results showed that this special catalyst NiO/CeO2 had high activity and stability for SMR reaction below 600°C. The stability of the catalyst reached more than 1000 hours. The conversion of methane under 590°C was above 90%. The tests of the influence of different H2O/CH4 mole ratios on activity and selectivity of catalyst showed that 1.5∼2.5 ratios were an ideal choice. During the running of micro-tube methane steam reformer with this catalyst, the methane conversion of 556°C kept over 25 mol.%.
    ECS Transactions 07/2015; 68(1):2775-2782. DOI:10.1149/06801.2775ecst
  • J J Wang · J M Hu · Ren-Ci Peng · Y Gao · Y Shen · L Q Chen · C W Nan ·
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    ABSTRACT: Voltage controlled 180° magnetization reversal has been achieved in BiFeO3-based multiferroic heterostructures, which is promising for the future development of low-power spintronic devices. However, all existing reports involve the use of an in-plane voltage that is unfavorable for practical device applications. Here, we investigate, using phase-field simulations, the out-of-plane (i.e., perpendicular to heterostructures) voltage controlled magnetism in heterostructures consisting of CoFe nanodots and (110) BiFeO3 thin film or island. It is predicted that the in-plane component of the canted magnetic moment at the CoFe/BiFeO3 interface can be reversed repeatedly by applying a perpendicular voltage across the bottom (110) BiFeO3 thin film, which further leads to an in-plane magnetization reversal in the overlaying CoFe nanodot. The non-volatility of such perpendicular voltage controlled magnetization reversal can be achieved by etching the continuous BiFeO3 film into isolated nanoislands with the same in-plane sizes as the CoFe nanodot. The findings would provide general guidelines for future experimental and engineering efforts on developing the electric-field controlled spintronic devices with BiFeO3-based multiferroic heterostructures.
    Scientific Reports 05/2015; 5:10459. DOI:10.1038/srep10459 · 5.58 Impact Factor
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    H. B. Huang · X. Q. Ma · J. J. Wang · Z. H. Liu · W. Q. He · L. Q. Chen ·
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    ABSTRACT: We developed a computational model to investigate the magnetic and structural phase transitions in metamagnetic shape memory alloys. The model combined the phase-field method with micromagnetic simulations. The model was used to calculate the transition temperature from ferromagnetic austenite to antiferromagnetic martensite, the Curie temperature, and their response to an external magnetic field, for the typical metamagnetic alloy NiCoMnIn. The calculated magnetization curves at different temperatures are consistent with reported experimental measurements. The simulations show that the walls of martensite twins are superimposed with the 90° magnetic domain walls of the low-temperature martensite phase, because of magnetostructural order parameter coupling.
    Acta Materialia 01/2015; 83:333–340. DOI:10.1016/j.actamat.2014.10.014 · 4.47 Impact Factor
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    H.B.HUang · X.Q.Ma · C.P.Zhao · Z.H.Liu · L.Q.Chen ·
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    ABSTRACT: We investigated the high power spin-torque oscillator in a half metallic Hensler alloy Co2MnSi spin valve nanopillars with perpendicular magnetization under external magnetic held using micromagnetic simulations. Our simulations show that the narrow optimum current of magnetization precession in the Heusler-based spin valve is broadened by introducing the surface anisotropy. The linear decrease of frequency with the out-of-plane magnetic held is obtained in our simulation. Additionally, the in-plane magnetic held dependence of frequency shows a parabolic curve which is explained by the magnetization trajectory tilting. Furthermore, we also discussed the decrease of output power using the excitation of non-uniform magnetization precession in the in-plane magnetic fields.
    Journal of Magnetism and Magnetic Materials 01/2015; 373:105. DOI:10.1016/j.jmmm.2014.03.050 · 1.97 Impact Factor
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    J J Wang · J M Hu · J Ma · J X Zhang · L Q Chen · C W Nan ·
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    ABSTRACT: Achieving 180° magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180° magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90° magnetization rotations, thereby leading to full 180° magnetization reversals.
    Scientific Reports 12/2014; 4:7507. DOI:10.1038/srep07507 · 5.58 Impact Factor
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    L.Chen, · F.Fan, · L. Hong, · J.Chen, · Y.Z.Ji, · S.L.Zhang, · T.Zhu, · L.Q.Chen, ·

    Journal of The Electrochemical Society 11/2014; 161(11):F3164. DOI:10.1149/2.0171411jes · 3.27 Impact Factor
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    H.B.Huang · J.M.Hu · T.N.Yang · X.Q.MA · L.Q.Chen ·
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    ABSTRACT: Effect of substrate misfit strain on current-induced in-plane magnetization reversal in CoFeB-MgO based magnetic tunnel junctions is investigated by combining micromagnetic simulations with phase-field microelasticity theory. It is found that the critical current density for in-plane magnetization reversal decreases dramatically with an increasing substrate strain, since the effective elastic field can drag the magnetization to one of the four in-plane diagonal directions. A potential strain-assisted multilevel bit spin transfer magnetization switching device using substrate misfit strain is also proposed. (C) 2014 AIP Publishing LLC.
    Applied Physics Letters 09/2014; 105(12):122407. DOI:10.1063/1.4896692 · 3.30 Impact Factor
  • H.-W. Zhang · Z. Liu · L. Liang · L. Chen · Y. Qi · S. J. Harris · P. Lu · L.-Q. Chen ·
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    ABSTRACT: Lithium (Li) dendrite formation compromises the reliability of Li-metal batteries, either because dendrite pieces lose electrical contract or growing dendrite penetrates the separator and leads to internal short-circuiting. In this paper, a nonlinear phase-field model is formulated to predict Li dendrite formation at the electrode/electrolyte interface. The phase field evolves by electrochemical reaction of which the rate depends on nonlinearly the thermodynamics driving force involving overpotential and ion concentration. A revised Poisson-Nesters-Planck Equation is further solved for ionic transport and local overpotential variation. The model is validated by 1-D fields distribution involving phase field, Lithium ion concentration and electrostatic potential. The 2-D tree-type lithium dendrite during Li deposition was produced if anisotropic surface energy is assumed. Finally, the 2D morphological evolution under different electrochemical conditions specified by the charging current density, and the anisotropy of surface energy was discussed.
    ECS Transactions 09/2014; 61(8):1-9. DOI:10.1149/06108.0001ecst
  • S.H. Zhou · Y. Wang · L.-Q. Chen · Z.-K. Liu · R.E. Napolitano ·
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    ABSTRACT: A solution-based thermodynamic description of the ternary Ni–Al–Mo system is developed here, incorporating first-principles calculations and reported modeling of the binary Ni–Al, Ni–Mo and Al–Mo systems. To search for the configurations with the lowest energies of the N phase, the Alloy Theoretic Automated Toolkit (ATAT) was employed and combined with VASP. The liquid, bcc and γ-fcc phases are modeled as random atomic solutions, and the γʹ-Ni3Al phase is modeled by describing the ordering within the fcc structure using two sublattices, summarized as (Al,Mo,Ni)0.75(Al,Mo,Ni)0.25. Thus, γ-fcc and γʹ-Ni3Al are modeled with a single Gibbs free energy function with appropriate treatment of the chemical ordering contribution. In addition, notable improvements are the following: first, the ternary effects of Mo and Al in the B2-NiAl and D0a-Ni3Mo phases, respectively, are considered; second, the N-NiAl8Mo3 phase is described as a solid solution using a three-sublattice model; third, the X-Ni14Al75Mo11 phase is treated as a stoichiometric compound. Model parameters are evaluated using first-principles calculations of zero-Kelvin formation enthalpies and reported experimental data. In comparison with the enthalpies of formation for the compounds ψ-AlMo, θ-Al8Mo3 and B2-NiAl, the first-principles results indicate that the N-NiAl8Mo3 phase, which is stable at high temperatures, decomposes into other phases at low temperature. Resulting phase equilibria are summarized in the form of isothermal sections and liquidus projections. To clearly identify the relationship between the γ-fcc and γʹ-Ni3Al phases in the ternary Ni–Al–Mo system, the specific γ-fcc and γʹ-Ni3Al phase fields are plotted in x(Al)–x(Mo)–T space for a temperature range 1200–1800 K.
    Calphad 09/2014; 46. DOI:10.1016/j.calphad.2014.03.002 · 1.37 Impact Factor
  • Y.Z. Ji · A. Issa · T.W. Heo · J.E. Saal · C. Wolverton · L.-Q. Chen ·
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    ABSTRACT: The precipitate morphology in Mg–rare earth (RE) element binary alloys is predicted using a multi-scale modeling approach combining a three-dimensional (3-D) phase-field model and first-principles density functional theory calculations. First-principles calculations provide all the required input parameters for the phase-field model, including lattice parameters, elastic constants, formation energies and interfacial energies. This integrated model is applied to a Mg–Nd alloy as a model system. Quantitative 3-D phase-field simulations are performed to study the metastable β′ precipitate morphologies, habit plane formation and spatial distribution of the precipitates during isothermal aging. The predicted morphologies of β′ precipitates are in excellent agreement with existing experimental observations. The influence of the precipitate morphology on the mechanical properties is also evaluated using the Orowan equation. The results are expected to provide guidance for achieving desirable precipitate morphologies and thus mechanical properties in Mg alloys.
    Acta Materialia 09/2014; 76:259–271. DOI:10.1016/j.actamat.2014.05.002 · 4.47 Impact Factor
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    ABSTRACT: We demonstrate that charge ordering can be quantitatively predicted by analyzing the Born effective charge (BEC), resolving the long-standing discrepancy between first-principles charge analysis and the nominal concepts of charge disproportionation in Fe3O4 and CaFeO3. In particular, the BEC differences between the disproportionated Fe ions are calculated to be similar to 2e, being in excellent agreement with the nominal charge separation in CaFeO3 while suggesting the charge disproportionation in Fe3O4 is understood by the charge separation similar to 2e instead of the nominal separation of similar to 1e.
    Chemical Physics Letters 06/2014; 607. DOI:10.1016/j.cplett.2014.05.044 · 1.90 Impact Factor
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    H.B. Huang · X.Q. Ma · Z.H. Liu · L.Q. Chen ·
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    ABSTRACT: We investigated the high-power spin-torque oscillator in a half-metallic Heusler alloy Co2MnSi spin-valve nanopillars with perpendicular magnetization using micromagnetic simulations. A stable high output power spin transfer precession was obtained in the condition of zero external magnetic field, and the narrow current of oscillation due to the high spin polarization of Heusler alloy is significantly widened by introducing the surface anisotropy. Furthermore, we discussed the current dependence of oscillation frequency and explained the blue frequency shift using the trajectories and spatial magnetic domains.
    Journal of Alloys and Compounds 06/2014; 597:230–235. DOI:10.1016/j.jallcom.2014.01.235 · 3.00 Impact Factor
  • H. Zhang · S.L. Shang · W.Y. Wang · Y. Wang · X.D. Hui · L.Q. Chen · Z.K. Liu ·
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    ABSTRACT: The structural and kinetic properties of Ni have been investigated between 300 and 2700 K using ab initio molecular dynamics within the framework of density-functional theory. Equations of state (EOS) are derived from the constant NVT ensembles with N being the number of atoms, V the volume, and T the temperature. From EOS fitting, the equilibrium volumes of Ni are predicted as a function of temperature, which are in good agreement with available experimental data. It is found that the solid-liquid phase transformation can be evaluated by the internal energy change and validated by the appearance of short-range ordering according to structural analysis. Additionally, the diffusion coefficient and shear viscosity are also predicted, in favorable accord with experimental data.
    Computational Materials Science 06/2014; 89. DOI:10.1016/j.commatsci.2014.03.031 · 2.13 Impact Factor
  • T.N. Yang · Jia-Mian Hu · C.W. Nan · L.Q. Chen ·
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    ABSTRACT: A phase-field model is developed to study local elastic coupling between magnetic and ferroelectric domains that show one-to-one pattern match. A multiferroic layered heterostructure of Co0.4Fe0.6/BaTiO3 is considered as an example. Dynamics of the local elastic coupling is investigated by simulating a time-dependent electric-field driven changes in local magnetization/polarization/strain distributions and by comparing the associated velocities of the magnetic and ferroelectric domain walls. It is found that the electric-field-driven dynamic magnetic domain evolution manifests itself as an alternating occurrence of local magnetization rotation and coupled motion of magnetic and ferroelectric domain walls with almost identical velocities.
    Applied Physics Letters 05/2014; 104(20):202402-202402-5. DOI:10.1063/1.4875719 · 3.30 Impact Factor
  • Y. Cao · J. Shen · C.A. Randall · L.Q. Chen ·
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    ABSTRACT: A self-consistent model has been proposed to study the switchable current-voltage (I-V) characteristics in Cu/BaTiO3/Cu sandwiched structure combining the phase-field model of ferroelectric domains and diffusion equations for ionic/electronic transport. The electrochemical transport equations and Ginzburg-Landau equations are solved using the Chebyshev collocation algorithm. We considered a single parallel plate capacitor configuration which consists of a single layer BaTiO3 containing a single tetragonal domain orientated normal to the plate electrodes (Cu) and is subject to a sweep of ac bias from −1.0 to 1.0 V at 25 °C. Our simulation clearly shows rectifying I-V response with rectification ratios amount to 102. The diode characteristics are switchable with an even larger rectification ratio after the polarization direction is flipped. The effects of interfacial polarization charge, dopant concentration, and dielectric constant on current responses were investigated. The switchable I-V behavior is attributed to the polarization bound charges that modulate the bulk conduction.
    Applied Physics Letters 05/2014; 104(18):182905-182905-5. DOI:10.1063/1.4875902 · 3.30 Impact Factor
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    H.B. Huang · X.Q. Ma · Z.H. Liu · C.P. Zhao · L.Q. Chen ·
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    ABSTRACT: We investigated the current-induced magnetization switching in a Heusler alloy Co2FeAl-based spin-valve nanopillar by using micromagnetic simulations. We demonstrated that the elimination of the intermediate state is originally resulted from the decease of effective magnetic anisotropy constant. The magnetization switching can be achieved at a small current density of 1.0 × 104 A/cm2 by increasing the demagnetization factors of x and y axes. Based on our simulation, we found magnetic anisotropy and demagnetization energies have different contributions to the magnetization switching.
    Journal of Applied Physics 04/2014; 115(13):133905-133905-5. DOI:10.1063/1.4870291 · 2.18 Impact Factor
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    J J Wang · J M Hu · T N Yang · M Feng · J X Zhang · L Q Chen · C W Nan ·
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    ABSTRACT: Voltage-modulated magnetism in magnetic/BiFeO3 heterostructures can be driven by a combination of the intrinsic ferroelectric-antiferromagnetic coupling in BiFeO3 and the antiferromagnetic-ferromagnetic exchange interaction across the heterointerface. However, ferroelectric BiFeO3 film is also ferroelastic, thus it is possible to generate voltage-induced strain in BiFeO3 that could be applied onto the magnetic layer across the heterointerface and modulate magnetism through magnetoelastic coupling. Here, we investigated, using phase-field simulations, the role of strain in voltage-controlled magnetism for these BiFeO3-based heterostructures. It is predicted, under certain condition, coexistence of strain and exchange interaction will result in a pure voltage-driven 180° magnetization reversal in BiFeO3-based heterostructures.
    Scientific Reports 04/2014; 4:4553. DOI:10.1038/srep04553 · 5.58 Impact Factor
  • T.N. Yang · Jia-Mian Hu · C.W. Nan · L.Q. Chen ·
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    ABSTRACT: A phase-field model coupled with constitutive equations is formulated to investigate the magnetoelectric cross-coupling in magnetic-ferroelectric composites. The model allows us to obtain equilibrium piezoelectric, piezomagnetic, dielectric, and magnetoelectric properties under a given magnetic or electric field, from the local distributions of polarization, magnetization, and strain in the composites. As an example, effective magnetoelectric coupling coefficient, i.e., magnetic-field-induced voltage output (or changes in polarization), of the CoFe2O4-BaTiO3 composites is numerically calculated. Influences of the phase connectivity and the phase fraction of the composites on the magnetoelectric coupling coefficient are discussed.
    Applied Physics Letters 02/2014; 104(5):052904-052904-5. DOI:10.1063/1.4863941 · 3.30 Impact Factor

Publication Stats

8k Citations
842.00 Total Impact Points


  • 2007-2015
    • Technical Institute of Physics and Chemistry
      Peping, Beijing, China
  • 1993-2015
    • Pennsylvania State University
      • Department of Materials Science and Engineering
      University Park, Maryland, United States
    • Rutgers, The State University of New Jersey
      • Department of Materials Science and Engineering
      New Brunswick, New Jersey, United States
  • 2013-2014
    • Tsinghua University
      • • State Key Laboratory of New Ceramics and Fine Processing
      • • School of Materials Science and Engineering
      Peping, Beijing, China
  • 1992-2013
    • William Penn University
      Worcester, Massachusetts, United States
  • 2011
    • National Chiao Tung University
      • Department of Material Science and Engineering
      Hsin-chu-hsien, Taiwan, Taiwan
    • Chonnam National University
      • Department of Material Science and Engineering
      Gwangju, Gwangju, South Korea
  • 2004-2007
    • Chinese Academy of Sciences
      • Institute of Physics
      Peping, Beijing, China