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https://www.readbyqxmd.com/read/28240913/stability-of-polar-vortex-lattice-in-ferroelectric-superlattices
#1
Zijian Hong, Anoop R Damodaran, Fei Xue, Shang-Lin Hsu, Jason Britson, Ajay K Yadav, Christopher T Nelson, Jianjun Wang, James Floyd Scott, Lane W Martin, Ramamoorthy Ramesh, Long-Qing Chen
A novel mesoscale state comprising of ordered polar vortex lattice has been demonstrated in ferroelectric superlattices of PbTiO3/SrTiO3. Here, we employ phase-field simulations, analytical theory, and experimental observations to evaluate thermodynamic conditions and geometric length scales that are critical for the formation of such exotic vortex states. We show that the stability of these vortex lattices involve an intimate competition between long-range electrostatic, long-range elastic, and short-range polarization gradient-related interactions leading to both an upper- and a lower- bound to the length scale at which these states can be observed...
February 27, 2017: Nano Letters
https://www.readbyqxmd.com/read/28240880/enhancement-of-ferroelectricity-for-orthorhombic-tb0-861mn0-121-mno3-%C3%AE-by-copper-doping
#2
Jianming Deng, Muhammad Asim Farid, Meng Zhang, Aimei Yang, Hongxing Zhang, Hao Zhang, Gengfang Tian, Meimei Wu, Laijun Liu, Junliang Sun, Guobao Li, Fuhui Liao, Jianhua Lin
Copper-doped (Tb0.861Mn0.121)MnO3-δ has been synthesized by the conventional solid state reaction method. X-ray, neutron, and electron diffraction data indicate that they crystallize in Pnma space group at room temperature. Two magnetic orderings are found for this series by neutron diffraction. One is the ICAM (incommensurate canted antiferromagnetic) ordering of Mn with a wave vector qMn = (∼0.283, 0, 0) with a ≈ 5.73 Å, b ≈ 5.31 Å, and c ≈ 7.41 Å, and the other is the CAM (canted antiferromagnetic) ordering of both Tb and Mn in the magnetic space group Pn'a21' with a ≈ 5...
February 27, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28240599/multiferroic-properties-of-the-pbtio-sub-3-sub-la-sub-2-3-sub-sr-sub-1-3-sub-mno-sub-3-sub-interface-studied-from-first-principles
#3
Vladislav Borisov, Sergey Ostanin, Ingrid Mertig
Magnetoelectric coupling and spin polarization at the multiferroic PbTiO<sub>3</sub>/La<sub>2/3</sub>Sr<sub>1/3</sub>MnO<sub>3</sub> (PTO/LSMO) interface is studied from first principles in view of the recent experimental observation of the tunneling magnetoresistance sign inversion in Co/PZT/LSMO tunnel junctions (D. Pantel <i>et al.</i>, Nat. Mater. <b>11</b>, 289 (2012)). Our results confirm the stabilization of the locally antiferromagnetic order in the manganite when the PTO polarization points away from the LSMO side, which changes the interface magnetization by 6...
February 27, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28239735/monte-carlo-simulation-of-magnetic-domain-structure-and-magnetic-properties-near-the-morphotropic-phase-boundary
#4
Songrui Wei, Sen Yang, Dong Wang, Xiaoping Song, Xiaoqin Ke, Yipeng Gao, Xiaoqi Liao, Yunzhi Wang
The morphotropic phase boundary (MPB), which is the boundary separating a tetragonal phase from a rhombohedral phase by varying the composition or mechanical pressure in ferroelectrics, has been studied extensively for decades because it can lead to strong enhancement of piezoelectricity. Recently, a parallel ferromagnetic MPB was experimentally reported in the TbCo2-DyCo2 ferromagnetic system and this discovery proposes a new way to develop potential materials with giant magnetostriction. However, the role of magnetic domain switching and spin reorientation near the MPB region is still unclear...
February 27, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28231005/synaptic-plasticity-selectively-activated-by-polarization-dependent-energy-efficient-ion-migration-in-an-ultrathin-ferroelectric-tunnel-junction
#5
Chansoo Yoon, Ji Hye Lee, Sangik Lee, Ji Hoon Jeon, Jun Tae Jang, Dae Hwan Kim, Young Heon Kim, Bae Ho Park
Selectively activated inorganic synaptic devices, showing a high on/off ratio, ultrasmall dimensions, low power consumption, and short programming time, are required to emulate the functions of high-capacity and energy-efficient reconfigurable human neural systems combining information storage and processing ( Li et al. Sci. Rep. 2014 , 4 , 4096 ). Here, we demonstrate that such a synaptic device is realized using a Ag/PbZr0.52Ti0.48O3 (PZT)/La0.8Sr0.2MnO3 (LSMO) ferroelectric tunnel junction (FTJ) with ultrathin PZT (thickness of ∼4 nm)...
February 24, 2017: Nano Letters
https://www.readbyqxmd.com/read/28229957/origins-and-mechanisms-of-hysteresis-in-organometal-halide-perovskites
#6
Cheng Li, Antonio Guerrero, Yu Zhong, Sven Huettner
Inorganic-organic organometal halide perovskites, such as CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> or CsPbI<sub>3</sub>, etc., are an unprecedented rising star in the field of photovoltaics since 2009, owing to its exceptionally high power conversion efficiency (PCE) and simple fabrication processability. Despite its relatively short history of development, intensive investigations have been concentrating on this material, ranging from crystal structure analysis and photophysical characterization, to performance optimization and device integration, etc...
February 23, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28225123/switchable-3-0-magnetoelectric-nanocomposite-thin-film-with-high-coupling
#7
Austin McDannald, Linghan Ye, Claudia Cantoni, Sreenivasulu Gollapudi, Gopalan Srinivasan, Bryan D Huey, Menka Jain
A mixed precursor solution method was used to deposit 3-0 nanocomposite thin films of PbZr0.52Ti0.48O3 (PZT) and CoFe2O4 (CFO). The piezoelectric behavior of PZT and magnetostrictive behavior of CFO allow for magnetoelectric (ME) coupling through strain transfer between the respective phases. High ME coupling is desired for many applications including memory devices, magnetic field sensors, and energy harvesters. The spontaneous phase separation in the 3-0 nanocomposite film was observed, with 25 nm CFO particle or nanophases distributed in discrete layers through the thickness of the PZT matrix...
February 22, 2017: Nanoscale
https://www.readbyqxmd.com/read/28221162/antiferromagnetic-spin-cantings-as-a-driving-force-of-ferroelectricity-in-multiferroic-cu-sub-2-sub-oseo-sub-3-sub
#8
Viacheslav Chizhikov, V Dmitrienko
Ferroelectric properties of cubic chiral magnet Cu<sub>2</sub>OSeO<sub>3</sub> can emerge due to the spin noncollinearity induced by antiferromagnetic cantings. The cantings are the result of the Dzyaloshinskii-Moriya interaction and in many ways similar to the ferromagnetic cantings in weak ferromagnets. An expression for the local electric polarization is derived, including terms with gradients of magnetization <b>M</b>(<b>r</b>). When averaged over the crystal the electric polarization has a non-vanishing part associated with the anisotropy of the crystal point group 23...
February 21, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28220861/electrically-tunable-metasurface-based-on-mie-type-dielectric-resonators
#9
Zhaoxian Su, Qian Zhao, Kun Song, Xiaopeng Zhao, Jianbo Yin
In this paper, we have designed a metasurface based on electrically tunable Mie-type resonators and theoretically demonstrated its tunable response to electromagnetic waves with varying frequency. The metasurface consists of disk-like ferroelectric resonators arrayed on a metal film and the upper surface of resonators is covered by ion gel film which is transparent for incident electromagnetic wave. Using the metal film and ion gel film as electrodes, the permittivity of the resonators can be adjusted by an external electric field and, as a result, the reflection phase of the resonators can be dynamically adjusted in a relatively wide range...
February 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28218895/ferroelectric-glass-of-spheroidal-dipoles-with-impurities-polar-nanoregions-response-to-applied-electric-field-and-ergodicity-breakdown
#10
Akira Onuki, Kyohei Takae
Using molecular dynamics simulation, we study dipolar glass in crystals composed of slightly spheroidal, polar particles and spherical, apolar impurities between metal walls. We present physical pictures of ferroelectric glass, which have been observed in relaxors, mixed crystals (such as KCN$_x$KBr$_{1-x}$), and polymers. Our systems undergo a diffuse transition in a wide temperature range, where we visualize polar nanoregions (PNRs) surrounded by impurities. In our simulation, the impurities form clusters and their space distribution is heterogeneous...
February 20, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28216672/enhancement-of-local-photovoltaic-current-at-ferroelectric-domain-walls-in-bifeo3
#11
Ming-Min Yang, Akash Bhatnagar, Zheng-Dong Luo, Marin Alexe
Domain walls, which are intrinsically two dimensional nano-objects exhibiting nontrivial electronic and magnetic behaviours, have been proven to play a crucial role in photovoltaic properties of ferroelectrics. Despite this recognition, the electronic properties of domain walls under illumination until now have been accessible only to macroscopic studies and their effects upon the conduction of photovoltaic current still remain elusive. The lack of understanding hinders the developing of nanoscale devices based on ferroelectric domain walls...
February 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28216653/dielectric-and-ferroelectric-sensing-based-on-molecular-recognition-in-cu-1-10-phenlothroline-2seo4%C3%A2-diol-systems
#12
Heng-Yun Ye, Wei-Qiang Liao, Qionghua Zhou, Yi Zhang, Jinlan Wang, Yu-Meng You, Jin-Yun Wang, Zhong-Ning Chen, Peng-Fei Li, Da-Wei Fu, Songping D Huang, Ren-Gen Xiong
The process of molecular recognition is the assembly of two or more molecules through weak interactions. Information in the process of molecular recognition can be transmitted to us via physical signals, which may find applications in sensing and switching. The conventional signals are mainly limited to light signal. Here, we describe the recognition of diols with Cu(1,10-phenlothroline)2SeO4 and the transduction of discrete recognition events into dielectric and/or ferroelectric signals. We observe that systems of Cu(1,10-phenlothroline)2SeO4·(diol) exhibit significant dielectric and/or ferroelectric dependence on different diol molecules...
February 20, 2017: Nature Communications
https://www.readbyqxmd.com/read/28209024/electric-field-control-of-magnetization-reorientation-in-co-pb-mg1-3nb2-3-pbtio3-heterostructure
#13
Fenglong Wang, Cai Zhou, Dunzhu Gesang, Changjun Jiang
Herein, we demonstrated an apparent electric field control of magnetization reorientation at room temperature, through a strain-mediated magnetoelectric coupling in ferromagnetic/ferroelectric (FM/FE) multiferroic heterostructure. As the applied electric field increased, the magnetization tended to deviate from the original direction, which was induced by nonlinear strain vs electric-field behavior from the ferroelectric substrates. Ferromagnetic resonance showed that the in-plane magnetic easy axis of the Co film was shifted sharply with electric field E = 10 kV/cm, which indicates that the in-plane uniaxial magnetic anisotropy of the Co film can be inverted via the application of an electric field...
December 2017: Nanoscale Research Letters
https://www.readbyqxmd.com/read/28207241/zero-thermal-expansion-and-semiconducting-properties-in-pbtio3-bi-co-ti-o3-ferroelectric-solid-solutions
#14
Zhao Pan, Jun Chen, Xingxing Jiang, Zheshuai Lin, Linxing Zhang, Longlong Fan, Yangchun Rong, Lei Hu, Hui Liu, Yang Ren, Xiaojun Kuang, Xianran Xing
Zero thermal expansion (ZTE) behavior is rare but important for both fundamental studies and practical applications of functional materials. Until now, most available ZTE materials are either electrical insulating oxides or conductive metallic compounds. Very few ZTE materials exhibit the semiconductor feature. Here we report a ZTE in a semiconducting ferroelectric of 0.6PbTiO3-0.4Bi(Co0.55Ti0.45)O3-δ. Its unit cell volume exhibits a negligible change over a broad temperature range from room temperature to 500 °C...
February 16, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28205559/crystalline-structure-defect-chemistry-and-room-temperature-colossal-permittivity-of-nd-doped-barium-titanate
#15
Qiaomei Sun, Qilin Gu, Kongjun Zhu, Rongying Jin, Jinsong Liu, Jing Wang, Jinhao Qiu
Dielectric materials with high permittivity are strongly demanded for various technological applications. While polarization inherently exists in ferroelectric barium titanate (BaTiO3), its high permittivity can only be achieved by chemical and/or structural modification. Here, we report the room-temperature colossal permittivity (~760,000) obtained in xNd: BaTiO3 (x = 0.5 mol%) ceramics derived from the counterpart nanoparticles followed by conventional pressureless sintering process. Through the systematic analysis of chemical composition, crystalline structure and defect chemistry, the substitution mechanism involving the occupation of Nd(3+) in Ba(2+) -site associated with the generation of Ba vacancies and oxygen vacancies for charge compensation has been firstly demonstrated...
February 13, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28205550/proton-tautomerism-for-strong-polarization-switching
#16
Sachio Horiuchi, Kensuke Kobayashi, Reiji Kumai, Shoji Ishibashi
Ferroelectrics based on proton tautomerism are promising in low-field and above-room-temperature operations. Here seven organic ferroelectric crystals are examined to search for efficient switching of strong spontaneous polarization on proton tautomerism. Solution-grown crystals exhibit strong pinning of ferroelectric domain walls, but excellent switching performance is awakened by depinning domain walls under thermal annealing and/or repetitive bipolar pulses with a high voltage. Compared with ferroelectric polymers such as polyvinylidefluoride, the optimized polarizations are comparable or stronger in magnitude whereas the coercive fields are two orders of magnitude weaker...
February 16, 2017: Nature Communications
https://www.readbyqxmd.com/read/28197560/tuning-the-band-gap-and-polarization-of-basno3-srsno3-superlattices-for-photovoltaic-applications
#17
Yajun Zhang, M P K Sahoo, Jie Wang
Band gap and polarization are two important quantities for enhancing the performance of photovoltaic materials. Based on first-principles calculations, we demonstrate that direct band gap and hybrid improper ferroelectric polarization coexist in BaSnO3/SrSnO3 superlattices. Furthermore, the band gap and polarization can be simultaneously tuned by mechanical strain and pressure. In the presence of tensile strain or negative pressure, the band gap is substantially lowered and the polarization is enhanced by about five times in comparison with that without mechanical loads...
February 15, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28195565/robust-ferromagnetism-carried-by-antiferromagnetic-domain-walls
#18
Hishiro T Hirose, Jun-Ichi Yamaura, Zenji Hiroi
Ferroic materials, such as ferromagnetic or ferroelectric materials, have been utilized as recording media for memory devices. A recent trend for downsizing, however, requires an alternative, because ferroic orders tend to become unstable for miniaturization. The domain wall nanoelectronics is a new developing direction for next-generation devices, in which atomic domain walls, rather than conventional, large domains themselves, are the active elements. Here we show that atomically thin magnetic domain walls generated in the antiferromagnetic insulator Cd2Os2O7 carry unusual ferromagnetic moments perpendicular to the wall as well as electron conductivity: the ferromagnetic moments are easily polarized even by a tiny field of 1 mT at high temperature, while, once cooled down, they are surprisingly robust even in an inverse magnetic field of 7 T...
February 14, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28195374/development-of-polar-order-by-liquid-crystal-self-assembly-of-weakly-bent-molecules
#19
Mohamed Alaasar, Marko Prehm, Silvio Poppe, Carsten Tschierske
Organic ferroelectrics are of growing importance for multifunctional materials. Here we provide an understanding of the distinct stages of the development of sterically induced polar order in liquid crystalline (LC) soft matter. Three series of weakly bent molecules derived from 4-cyanoresorcinol as the bent core unit with laterally fluorinated azobenzene wings have been synthesized and the effects of the position of fluorine substitution, alkyl chain length and temperature on the LC self-assembly and polar order were studied...
February 13, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28193560/electron-beam-induced-current-and-active-secondary-electron-voltage-contrast-with-aberration-corrected-electron-probes
#20
Myung-Geun Han, Joseph A Garlow, Matthew S J Marshall, Amanda L Tiano, Stanislaus S Wong, Sang-Wook Cheong, Frederick J Walker, Charles H Ahn, Yimei Zhu
The ability to map out electrostatic potentials in materials is critical for the development and the design of nanoscale electronic and spintronic devices in modern industry. Electron holography has been an important tool for revealing electric and magnetic field distributions in microelectronics and magnetic-based memory devices, however, its utility is hindered by several practical constraints, such as charging artifacts and limitations in sensitivity and in field of view. In this article, we report electron-beam-induced-current (EBIC) and secondary-electron voltage-contrast (SE-VC) with an aberration-corrected electron probe in a transmission electron microscope (TEM), as complementary techniques to electron holography, to measure electric fields and surface potentials, respectively...
February 6, 2017: Ultramicroscopy
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