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Ferrimagnetism and abnormal spin lattice coupling in dilute magnetic ferroelectric (Bi_(0.46) Na_(0.46) Ba_(0.08))TiO_3:Co

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Chinese Physics B 2011年第2期20卷 487-494页

作者：范婧董新伟宋友王克锋刘俊明江向平 laboratory of solid state microstructures Nanjing University International Center for materials Physics Chinese Academy of Sciences department of Material science and engineering Jingdezhen Ceramic Institute

We have investigated the low-temperature magnetism and spin-lattice coupling in （***）TiO3 ：Co in order to understand the magnetoelectric effect in such artificially synthesized dilute magnetic ferroelectrics. It is revealed that the as-prepared （***）TiO3：Co at Co content of 20%~30% exhibits fascinating ferrimagnetism which is robust against magnetic field, the abnormal spin lattice coupling characterized by a negative magnetostriction effect; and the suppressed magnetic moment within the temperature range of 30 K-50 K is identified. These magnetic behaviours at low temperatures can be explained by the competition between the ferrimagnetic response and the magnetic moment suppression induced by the abnormal spin lattice coupling effect. Finally, the ferroelectric and magnetodielectric properties are also discussed.

关键词： ferrimagnetics magnetostriction ferroelectricity

Highly stretchable and sensitive strain sensor based on silver nanowires/carbon nanotubes on hair band for human motion detection

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Progress in Natural science:materials International 2021年第3期31卷 379-386页

作者： Yanqiang Cao Tiancheng Lai Furui Teng Chang Liu Aidong Li national laboratory of solid state microstructures Materials Science and Engineering Department College of Engineering and Applied Sciences Collaborative Innovation Center of Advanced Microstructures Nanjing University Institute of Micro-nano Photonic & Beam Steering School of Science Nanjing University of Science and Technology

In this work, a highly stretchable and sensitive strain sensor using silver nanowires(Ag NWs)/multi-walled carbon nanotubes(MWCNTs) on hair band is proposed. The fabrication process of such sensors enabled scalable and facile production with low cost by dipping hair band into Ag NWs/MWCNTs composites suspension. The sensing performance of the sensors was optimized by tuning the Ag NWs/MWCNTs mass ratio. The hair band based strain sensor with Ag NWs/MWCNTs mass ratio of 30 exhibited the best performance with high sensitivity of 416.0 and good stretchability up to 70%. Moreover, great repeatability and long-term stability could be achieved over 7500 cycles of stretch-release. This Ag NWs/MWCNTs-hair band sensor can be used for monitoring human motions and swallowing action.

关键词： Carbon nanotubes Silver nanowires Strain sensor Stretchable electronics Human motion detection

Simultaneously enhanced moisture tolerance and defect passivation of perovskite solar cells with cross-linked grain encapsulation

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Journal of Energy Chemistry 2021年第5期30卷 455-462页

作者： Ke Xiao Qiaolei Han Yuan Gao Shuai Gu Xin Luo Renxing Lin Jia Zhu Jun Xu Hairen Tan national laboratory of solid state microstructures Jiangsu Key Laboratory of Artificial Functional MaterialsCollege of Engineering and Applied SciencesNanjing UniversityNanjing 210093JiangsuChina School of Electronics science and engineering Nanjing UniversityNanjing 210093JiangsuChina

The grain surfaces(film surface and grain boundary)of polycrystalline perovskite films are vulnerable sites in solar cells since they pose a high defect density and initiate the degradation of perovskite *** simultaneously defect passivation and grain protection from moisture is crucial for the viability of perovskite solar ***,an in situ cross-linked grain encapsulation(CLGE)strategy that improves both device stability and defect passivation is ***-linkable semiconducting small molecules are mixed into the antisolvent to uniformly form a compact and conducting cross-linked layer over the grain *** cross-linked coating layer not only passivates trap states and facilitates hole extraction,but also enhances the device stability by preventing moisture *** the CLGE strategy,a high power conversion efficiency(PCE)of 22.7%is obtained in 1.55-eV bandgap planar perovskite solar *** unencapsulated devices with CLGE exhibit significantly enhanced device stability again moisture and maintain>90%of their initial PCE after shelf storage under ambient condition for over10,000 h.

关键词： Perovskite solar cell Cross-link Defect passivation Stability Moisture tolerance

Creation and erasure of polar bubble domains in PbTiO_(3)films by mechanical stress and light illuminations

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Journal of Materiomics 2023年第4期9卷 626-633页

作者： Xingchen Zhang Hongying Chen Guo Tian Wenda Yang Zhen Fan Zhipeng Hou Deyang Chen Min Zeng Minghui Qin Jinwei Gao Xingsen Gao Jun-Ming Liu Guangdong Provincial Key laboratory of Quantum engineering and Quantum materials and Institute for Advanced materials South China Academy of Advanced OptoelectronicsSouth China Normal UniversityGuangzhou510006China laboratory of solid-state microstructures and Innovation Center of Advanced microstructures Nanjing UniversityNanjing210093China national laboratory of solid state microstructures Department of Materials Science and EngineeringJiangsu Key Laboratory of Artificial Functional MaterialsNanjing UniversityNanjing210093China

The controllable manipulation of polar topological structures(*** bubble)in ferroelectric materials have been considered as a cornerstone for future programmable ***,we present the effective creation and erasure of polar bubble states PbTiO_(3)(PTO)multilayers trigged by mechanical stress and light illumination,*** was found that applying atomic force microscope(AFM)tip force can induced formation of nanoscale bubble domains from the initial monodomain ***,the created bubble domain can be eliminated by exposure to ultraviolet or infrared light *** above results can be understood by modulation of depolarization screening charges and bias fields,as reflected by scanning Kelvin potential microscopic(SKPM)observations,whereby the flexoelectric effect from the tip force tends to remove the screening charges on top surface and modulate the bias field that favors the formation of bubble state while light illumination tends to recover the screen charges and favor the monodomain *** results provide a good example for multi-field manipulation of polar topologies,which might create a new avenue towards the immerging new concept electronic devices.

关键词： Ferroelectric films Polar topologies Piezoresponse force microscopy

Graphene-like physics in optical lattices

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Chinese Physics B 2013年第11期22卷 114-124页

作者：梅锋张丹伟朱诗亮 national laboratory of solid state microstructures and School of Physics Nanjing University laboratory of Quantum engineering and Quantum materials School of Physics and Telecommunication Engineering South China Normal University

Graphene has attracted enormous attention over the past years in condensed matter physics. The most interesting feature of graphene is that its low-energy excitations are relativistic Dirac fermions. Such feature is the origin of many topological properties in graphene-like physics. On the other hand, ultracold quantum gas trapped in an optical lattice has become a unique setting for quantum simulation of condensed matter physics. Here, we mainly review our recent work on quantum simulation of graphene-like physics with ultracold atoms trapped in a honeycomb or square optical lattice, including the simulation of Dirac fermions and quantum Hall effect with and without Landau levels. We also present the related experimental advances.

关键词： graphene Dirac fermions quantum Hall effect optical lattice

Recent progress on magnetic-field studies on quantum-spin-liquid candidates

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Chinese Physics B 2018年第10期27卷 1-14页

作者： Zhen Ma Kejing Ran Jinghui Wang Song Bao Zhengwei Cai Shichao Li Jinsheng Wen national laboratory of solid state microstructures and department of Physics Nanjing UniversityNanjing 210093China Collaborative Innovation Center of Advanced microstructures Nanjing UniversityNanjing 210093China

Quantum spin liquids（QSLs） represent a novel state of matter in which quantum fluctuations prevent the conventional magnetic order from being established, and the spins remain disordered even at zero temperature. There have been many theoretical developments proposing various QSL states. On the other hand, experimental movement was relatively slow largely due to limitations on the candidate materials and difficulties in the measurements. In recent years, the experimental progress has been accelerated. In this topical review, we give a brief summary of experiments on the QSL candidates under magnetic fields. We arrange our discussions by two categories： i） Geometrically-frustrated systems, including triangularlattice compounds YbMgGaO4 and YbZnGaO4, κ-（BEDT-TTF）2 Cu2（CN）3, and EtMe3 Sb[Pd（dmit）2]2, and the kagom′e system ZnCu3（OH）6 Cl2; ii） the Kitaev material α-RuCl3. Among these, we will pay special attention to α-RuCl3, which has been intensively studied by ours and other groups recently. We will present evidence that both supports and rejects the QSL ground state for these materials, based on which we give several perspectives to stimulate further research activities.

关键词： quantum spin liquids spin glass neutron scattering

Structural,spectroscopic,and dielectric characterizations of Mn-doped 0.67BiFeO_(3)-0.33BaTiO_(3)multiferroic ceramics

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Journal of Advanced Ceramics 2013年第3期2卷 252-259页

作者： Qiming HANG Wenke ZHOU Xinhua ZHU Jianmin ZHU Zhiguo LIU Talaat AL-KASSAB national laboratory of solid state microstructures School of PhysicsNanjing UniversityNanjing 210093China national laboratory of solid state microstructures Department of Materials Science and EngineeringNanjing UniversityNanjing 210093China King Abdullah university of science&Technology(KAUST) Physical Sci.and Eng.Thuwal 23955-6900Kingdom of Saudi Arabia

0.67BiFeO_(3)-0.33BaTiO_(3)multiferroic ceramics doped with x mol%MnO_(2)(x=2-10)were synthesized by solid-state *** formation of a perovskite phase with rhombohedral symmetry was confirmed by X-ray diffraction(XRD).The average grain sizes were reduced from 0.80mm to 0.50mm as increasing the Mn-doped *** crystalline nature of the grains was revealed by high-resolution transmission electron microscopy(HRTEM)images and electron diffraction *** nano-sized ferroelectric domains with an average size of 9 nm randomly distributed in the ceramic samples were revealed by TEM *** domain lamellae(71°ferroelectric domains)with an average width of 5 nm were also *** modes were examined by Raman spectra,where only four Raman peaks at 272 cm^(-1)(E-4 mode),496 cm^(-1)(A_(1)-4 mode),639 cm^(-1),and 1338 cm^(-1)were *** blue shifts in the E-4 and A_(1)-4 Raman mode frequencies were interpreted by a spring oscillator *** dieletric constants of the present ceramics as a function of the Mn-doped levels exhibited a V-typed *** were in the range of 350-700 measured at 10^(3)Hz,and the corresponding dielectric losses were in range of 0.43-0.96,approaching to 0.09 at 10^(6)Hz.

关键词： multiferroic ceramics dielectric properties Raman spectra microstructure

Blue-Light Emission from Nanocrystalline La_(0.5)Na_(0.5)TiO^(3)

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Chinese Physics Letters 1998年第10期15卷 758-760页

作者： ZHANG Wei-feng ZHANG Xing-tang YIN Zhen ZHANG Ming-sheng MA Guo-hong DU Zu-liang Center for materials Analysis and national laboratory of solid state microstructures Nanjing UniversityNanjing 210093 department of Physics He’nan UniversityKaifeng 475001

Nanocrystalline La_(0.5)Na_(0.5)TiO^(3) powders were prepared by the stearic acid-gel method,and the grain sizes could be controlled by varying annealing *** sizes were determined to be from 14 to 50nm using Scherrer's formula.A very strong blue-light emission band around 480nm was clearly observed in the nano-sized La_(0.5)Na_(0.5)TiO^(3) with a grain size of 14nm at room ***,nano-size effects on the luminescence properties were *** results could be explained with the aid of a self-trapped exciton model.

关键词： temperature. sizes sized

Comparative study of vortex dynamics in CaKFe_4As_4 and Ba_(0.6)K_(0.4)Fe_2As_2 single crystals

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science Bulletin 2019年第2期64卷 81-90页

作者： Wang Cheng Hai Lin Bing Shen Hai-Hu Wen Center for Superconducting Physics and materials National Laboratory of Solid State Microstructures and Department of Physics National Center of Microstructures and Quantum Manipulation Nanjing University School of Physics Sun Yat-sen University

We investigate the vortex dynamics in two typical hole doped iron based superconductors CaKFe_4As_4(CaK1144) and Ba_(0.6)K_(0.4)Fe_2As_2(BaK122) with similar superconducting transition temperatures. It is found that the magnetization hysteresis loop exhibits a clear second peak effect in BaK122 in wide temperature region while it is absent in CaK1144. However, a second peak effect of critical current density versus temperature is observed in CaK1144, which is however absent in BaK122. The different behaviors of second peak effect in BaK122 and CaK1144 may suggest distinct origins of vortex pinning in different systems. Magnetization and its relaxation have also been measured by using dynamical and conventional relaxation methods for both systems. Analysis and comparison of the two distinct systems show that the vortex pinning is stronger and the critical current density is higher in BaK122 system. It is found that the Maley's method can be used and thus the activation energy can be determined in BaK122 by using the time dependent magnetization in wide temperature region, but this is not applicable in CaK1144 *** we present the different regimes with distinct vortex dynamics in the field-temperature diagram for the two systems.

关键词： CaKFe4As4 Ba0.6K0.4Fe2As2 Magnetization hysteresis loop Vortex pinning Second peak effect Vortex dynamics