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J.-M. Liu

Bio: J.-M. Liu is an academic researcher from Nanjing University. The author has contributed to research in topics: Ferroelectricity & Dielectric. The author has an hindex of 35, co-authored 309 publications receiving 7661 citations. Previous affiliations of J.-M. Liu include South China Normal University & Huazhong University of Science and Technology.


Papers
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TL;DR: In this article, the authors highlight the physical concepts of multiferroicity and the current challenges to integrate the magnetism and ferroelectricity into a single-phase system, and summarize various strategies used to combine the two types of orders.
Abstract: Multiferroics, defined for those multifunctional materials in which two or more kinds of fundamental ferroicities coexist, have become one of the hottest topics of condensed matter physics and materials science in recent years. The coexistence of several order parameters in multiferroics brings out novel physical phenomena and offers possibilities for new device functions. The revival of research activities on multiferroics is evidenced by some novel discoveries and concepts, both experimentally and theoretically. In this review article, we outline some of the progressive milestones in this stimulating field, specially for those single phase multiferroics where magnetism and ferroelectricity coexist. Firstly, we will highlight the physical concepts of multiferroicity and the current challenges to integrate the magnetism and ferroelectricity into a single-phase system. Subsequently, we will summarize various strategies used to combine the two types of orders. Special attentions to three novel mechanisms for multiferroicity generation: (1) the ferroelectricity induced by the spin orders such as spiral and E-phase antiferromagnetic spin orders, which break the spatial inversion symmetry, (2) the ferroelectricity originating from the charge ordered states, and (3) the ferrotoroidic system, will be paid. Then, we will address the elementary excitations such as electromagnons, and application potentials of multiferroics. Finally, open questions and opportunities will be prospected.

1,088 citations

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TL;DR: In this article, a single-phased ferroelectromagnet BiFeO3 ceramics with high resistivity were synthesized by a rapid liquid phase sintering technique.
Abstract: Single-phased ferroelectromagnet BiFeO3 ceramics with high resistivity were synthesized by a rapid liquid phase sintering technique. Saturated ferroelectric hysteresis loops were observed at room temperature in the ceramics sintered at 880 °C for 450 s. The spontaneous polarization, remnant polarization, and the coercive field are 8.9 μC/cm2, 4.0 μC/cm2, and 39 kV/cm, respectively, under an applied field of 100 kV/cm. It is proposed that the formation of Fe2+ and an oxygen deficiency leading to the higher leakage can be greatly suppressed by the very high heating rate, short sintering period, and liquid phase sintering technique. The latter was also found effective in increasing the density of the ceramics. The sintering technique developed in this work is expected to be useful in synthesizing other ceramics from multivalent or volatile starting materials.

970 citations

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TL;DR: In this article, single-phase Bi1−xNdxFeO3 (BNFOx) multiferroic ceramics were prepared to study the effects of Nd substitution on their crystal structure and ferroelectromagnetic behavior.
Abstract: Single-phase Bi1−xNdxFeO3 (BNFOx) (x=0–02) multiferroic ceramics were prepared to study the effects of Nd substitution on their crystal structure and ferroelectromagnetic behavior Rietveld refinement of x-ray diffraction data showed a continual transformation of crystal structure from the rhombohedral structure of BNFOx=0 (BiFeO3) to a triclinic structure in BNFOx=005–015 and a pseudotetragonal structure in BNFOx=0175–02 Ferroelectromagnetic measurements revealed the existence of ferroelectricity with remnant polarization of ∼9μC∕cm2 in BNFOx=0–0175, paraelectricity in BNFOx=02, and weak ferromagnetism with remnant magnetizations of 007–0227emu∕g in BNFOx=015–02 Magnetoelectric coupling was obvious in BNFOx=015–0175 near the Neel temperature of ∼380°C

468 citations

Journal ArticleDOI
TL;DR: In this article, the authors present the results of a systematic study on how the processing conditions of spin casting affect the morphology of polymer thin films, and how the morphology affects polymer light-emitting diode (LED) performance.
Abstract: We present the results of a systematic study on how the processing conditions of spin casting affect the morphology of polymer thin films, and how the morphology affects polymer light-emitting diode (LED) performance. The absorption peaks of poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1, 4-phenylene vinylene) (MEH-PPV) thin films, which reflects the conjugation of π electrons, are strongly correlated to the spin-casting conditions. At high spin speed, better conjugation is observed. In addition, the photoluminescence emission peak of MEH-PPV films at ∼630 nm has a strong correlation to polymer aggregation. By proper selection of organic solvents, polymer solution concentrations, and spin speeds, we are able to control the aggregation of the polymer chains. Subsequently, we are able to control the emission color and the quantum efficiency of the MEH-PPV LEDs by simply adjusting the spin-casting conditions. Although spin casting is the most commonly used technique for the preparation of polymer thin films, our fin...

357 citations

Journal ArticleDOI
TL;DR: In this article, perovskite-type polycrystalline BiFeO3 (BFO) nanowires were synthesized using the anodized alumina template technique.
Abstract: Perovskite-type polycrystalline BiFeO3 (BFO) nanowires (∼50nm in diameter and ∼5μm in length) were synthesized using the anodized alumina template technique. An energy band gap of ∼2.5eV was determined from the UV-visible diffuse reflectance spectrum, and its photocatalytic ability to produce O2 was revealed under UV irradiation. Weak ferromagnetism at room temperature and superparamagnetism at low temperature were observed for the BFO nanowires, different from the antiferromagnetic order in bulk BFO, reflecting the significant size effects on the magnetic ordering of BFO.

340 citations


Cited by
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TL;DR: Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency as mentioned in this paper, and many DSC research groups have been established around the world.
Abstract: Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

8,707 citations

Journal ArticleDOI
TL;DR: In this paper, the authors summarize both the basic physics and unresolved aspects of BiFeO3 and device applications, which center on spintronics and memory devices that can be addressed both electrically and magnetically.
Abstract: BiFeO3 is perhaps the only material that is both magnetic and a strong ferroelectric at room temperature. As a result, it has had an impact on the field of multiferroics that is comparable to that of yttrium barium copper oxide (YBCO) on superconductors, with hundreds of publications devoted to it in the past few years. In this Review, we try to summarize both the basic physics and unresolved aspects of BiFeO3 (which are still being discovered with several new phase transitions reported in the past few months) and device applications, which center on spintronics and memory devices that can be addressed both electrically and magnetically.

3,526 citations

Journal ArticleDOI
TL;DR: In this article, a review of mostly recent activities can be found, with a brief summary of the historical perspective of the multiferroic magnetoelectric composites since its appearance in 1972.
Abstract: Multiferroic magnetoelectric materials, which simultaneously exhibit ferroelectricity and ferromagnetism, have recently stimulated a sharply increasing number of research activities for their scientific interest and significant technological promise in the novel multifunctional devices. Natural multiferroic single-phase compounds are rare, and their magnetoelectric responses are either relatively weak or occurs at temperatures too low for practical applications. In contrast, multiferroic composites, which incorporate both ferroelectric and ferri-/ferromagnetic phases, typically yield giant magnetoelectric coupling response above room temperature, which makes them ready for technological applications. This review of mostly recent activities begins with a brief summary of the historical perspective of the multiferroic magnetoelectric composites since its appearance in 1972. In such composites the magnetoelectric effect is generated as a product property of a magnetostrictive and a piezoelectric substance. A...

3,288 citations

Journal ArticleDOI
TL;DR: Baxter has inherited the mantle of Onsager who started the process by solving exactly the two-dimensional Ising model in 1944 as mentioned in this paper, and there has been a growing belief that all the twodimensional lattice statistical models will eventually be solved and that it will be Professor Baxter who solves them.
Abstract: R J Baxter 1982 London: Academic xii + 486 pp price £43.60 Over the past few years there has been a growing belief that all the twodimensional lattice statistical models will eventually be solved and that it will be Professor Baxter who solves them. Baxter has inherited the mantle of Onsager who started the process by solving exactly the two-dimensional Ising model in 1944.

1,658 citations