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Featured researches published by Meng-Qiu Cai.


Journal of Applied Physics | 2011

Magnetoelectric effect and critical thickness for ferroelectricity in Co/BaTiO3/Co multiferroic tunnel junctions

Dan Cao; Meng-Qiu Cai; Wang Yu Hu; Chun-Mei Xu

Based on first-principles calculations, the magnetoelectric effect and the critical thickness for ferroelectricity in Co/BaTiO3/Co multiferroic tunnel junctions were investigated. The calculated results show that the ferroelectricity of multiferroic tunnel junctions can be maintained until a critical thickness of 1.6 nm. The magnetic moments of interface atoms are sensitive to the ferroelectric displacements, which leads to a sizable magnetoeletric effect in multiferroic tunnel junctions. The multiferroic tunnel junctions may opens an avenue for the development of novel electronic devices.


Applied Physics Letters | 2011

Uniaxial strain-modulated conductivity in manganite superlattice (LaMnO3/SrMnO3)

Dan Cao; Meng-Qiu Cai; W. Y. Hu; Jun Peng; Yue Zheng; Haitao Huang

We have investigated the magnetic ordering and electrical conductivity transitions of (LaMnO3)2/(SrMnO3)2 superlattices grown on SrTiO3 substrate based on density-functional theory. It is found that the uniaxial tensile strain along the z axis of about 1.4% induced a magnetic transition from antiferromagnetic to ferromagnetic ordering. At the interface the orbital order changes from a combination of x2−y2 and 3z2−r2 to x2−y2 as strain becomes more compressive; as a result the electrical transport is transformed from three-dimensions to two-dimensions at the high uniaxial compressive strain. Our results suggest that the out-of-plane electrical conductivity can be modulated and controlled by uniaxial strain.


Applied Physics Letters | 2010

Phase diagram of ferroelectric nanowires and its mechanical force controllability

Shaopeng Lin; Yue Zheng; Meng-Qiu Cai; Biao Wang

A phenomenological thermodynamic model of ferroelectric nanowires is developed to investigate the size-temperature phase diagrams. Considering existence of the surface tension, size, and external applied stress effects, the approximated expressions of the transition temperatures at which the paraelectric phase loses its stability with respect to the appearance of the spontaneous polarization are derived. At the same time, the size-temperature phase diagrams as functions of the ferroelectric nanowire radius are obtained, and also show its external mechanical stress controllability.


Applied Physics Letters | 2011

First-principles study of the critical thickness in asymmetric ferroelectric tunnel junctions

Meng-Qiu Cai; Yong Du; Bo-Yun Huang

The absent critical thickness of fully relaxed asymmetric ferroelectric tunnel junctions is investigated by first-principles calculations. The results show that PbTiO3 thin film between Pt and SrRuO3 electrodes can still retain a significant and stable polarization down to thicknesses as small as 0.8 nm, quite unlike the case of symmetric ferroelectric tunnel junctions. We trace this surprising result to the generation of a large electric field by the charge transfer between the electrodes caused by their different electronic environments, which acts against the depolarization field and enhances the ferroelectricity, leading to the reduction, or even complete elimination, for the critical thickness.


Journal of Applied Physics | 2010

Anisotropy of the electrical transport properties in a Ni2MnGa single crystal: Experiment and theory

Min Zeng; Meng-Qiu Cai; Siu Wing Or; Helen Lai Wa Chan

Electrical transport properties in ferromagnetic shape memory Ni–Mn–Ga single crystal have been investigated both in experiment and theory by analyzing electrical resistivity along different crystallographic directions during heating. The experimental results show a clear first-order martensitic transformation and a large anisotropic resistivity (AR) of 23.7% at the tetragonal martensitic phase. The theoretical conductivity (σ=1/ρ), estimated using first-principles calculations combined with classical Boltzman transport theory, proves essential crystallographic anisotropic resistivity (AR=31%) in the martensitic phase and agrees well with experimental results. The AR in the martensitic phase is reveled to mainly originate from the splitting of the minority-spin Niu20023d and Gau20024p states near the Fermi level and hence reconstruction of the minority-spin Fermi surface upon martensitic transformation.


Solid State Communications | 2009

First-principles study on the electronic and optical properties of BiFeO3

Hai Wang; Yue Zheng; Meng-Qiu Cai; Haitao Huang; Helen L. W. Chan


Physical Chemistry Chemical Physics | 2011

Vacancy-induced magnetism in BaTiO3(001) thin films based on density functional theory

Dan Cao; Meng-Qiu Cai; W. Y. Hu; Ping Yu; Haitao Huang


Solid State Communications | 2011

Effect of nitrogen doping on optical properties and electronic structures of SrZrO3 films

Chunhong Tang; Xiaomei Lu; Fengzhen Huang; Meng-Qiu Cai; Yi Kan; Xiaofei Wang; Chao Zhang; Jinsong Zhu


Solid State Communications | 2009

First-principles study on the electronic and optical properties of BiFeO 3

Hai Wang; Yue Zheng; Meng-Qiu Cai; Haitao Huang; Helen Lai-Wa Chan


Solid State Communications | 2009

Joint experiment and theory to study the band structure of SrZrO3 in orthorhombic phase

Chunhong Tang; Xiaomei Lu; Fengzhen Huang; Meng-Qiu Cai; Xin Wu; Ruwen Pen; Jinsong Zhu

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Yue Zheng

Sun Yat-sen University

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Haitao Huang

Hong Kong Polytechnic University

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Yong Du

Central South University

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Hai Wang

Hong Kong Polytechnic University

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