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Full-Text Articles in Physical Sciences and Mathematics

Reduction Of Superconducting Transition Temperature And Flux Pinning In Al And C Codoped Mgb2 With Insight From First-Principles Calculations, Aihua Li, Xiaolin Wang, S X. Dou, Qiwen Yao, Zhenxiang Cheng, Saeid Soltanian, J M. Yoo, P Munroe Jan 2008

Reduction Of Superconducting Transition Temperature And Flux Pinning In Al And C Codoped Mgb2 With Insight From First-Principles Calculations, Aihua Li, Xiaolin Wang, S X. Dou, Qiwen Yao, Zhenxiang Cheng, Saeid Soltanian, J M. Yoo, P Munroe

Australian Institute for Innovative Materials - Papers

We report for the first time the Al and C codoping effect on the structures and superconductivity in MgB2. It was found that both the lattice parameters and the Tc decreased monotonically with increasing doping level of both Al and C. The Tc dropped to 27.5 and 7 K for x=0.2 and for x =0.4, respectively. The reduction of Tc for the codoping was found to be quicker than for individual Al doping and slower than for individual C doping at the same doping levels. First-principles calculations indicated that the observed decrease in Tc …


Antiferromagnetic Transition In Eufe2as2: A Possible Parent Compound For Superconductors, Zhi Ren, Zengwei Zhu, Shuai Jiang, Xiangfan Xu, Qian Tao, Cao Wang, Chunmu Feng, Guanghan Cao, Zhu An Xu Jan 2008

Antiferromagnetic Transition In Eufe2as2: A Possible Parent Compound For Superconductors, Zhi Ren, Zengwei Zhu, Shuai Jiang, Xiangfan Xu, Qian Tao, Cao Wang, Chunmu Feng, Guanghan Cao, Zhu An Xu

Australian Institute for Innovative Materials - Papers

Ternary iron arsenide EuFe2 As2 with ThCr2 Si2 -type structure has been studied by magnetic susceptibility, resistivity, thermopower, Hall, and specific-heat measurements. The compound undergoes two magnetic phase transitions at about 200 and 20 K, respectively. The former was found to be accompanied with a slight drop in magnetic susceptibility (after subtracting the Curie-Weiss paramagnetic contribution), a rapid decrease in resistivity, a large jump in thermopower, and a sharp peak in specific heat with decreasing temperature, all of which point to a spin-density-wave-like antiferromagnetic transition. The latter was proposed to be associated with an A -type antiferromagnetic ordering of Eu2+ …


Gel Sensors And Actuators, Paul Calvert Jan 2008

Gel Sensors And Actuators, Paul Calvert

Australian Institute for Innovative Materials - Papers

Gels, soft polymeric or composite materials that have a high fraction of water, are often found as structural materials and actuators in nature but have so far not found many uses when fabricated synthetically. We first examine some natural systems such as jellyfish, sea anemones, starfish, legumes, and human tissue, all having interesting ways of moving or otherwise reacting to the surrounding environment. Then we discuss swelling and cross-linking of hydrogels, followed by a look at actuation by electrically, thermally, and chemically stimulated gels, noting that electrical stimulation needs a chemical intermediary to show substantial actuation (comparable to human muscle, …


La And Nb Codoped Bifeo3 Multiferroic Thin Films On Lanio3/Si And Iro2/Si Substrates, Zhenxiang Cheng, Xiaolin Wang, Hideo Kimura, Kiyoshi Ozawa, S X. Dou Jan 2008

La And Nb Codoped Bifeo3 Multiferroic Thin Films On Lanio3/Si And Iro2/Si Substrates, Zhenxiang Cheng, Xiaolin Wang, Hideo Kimura, Kiyoshi Ozawa, S X. Dou

Australian Institute for Innovative Materials - Papers

Nb and La codoped BiFeO3 thin films were fabricated on oxide bottom electrodes, LaNiO3/Si and IrO2/Si, by pulsed laser deposition method. The doped BiFeO3 thin film capacitor on LaNiO3showed a remnant polarization of more than 75 µC/cm2 in a saturated hysteresis loop. The same La and Nb codoped BiFeO3 thin film capacitors on IrO2 showed a larger remnant polarization, while with a significant contribution from the leakage current. Furthermore, the doped BiFeO3 capacitor on the LaNiO3 bottom electrode showed worse fatigue resistance than the film on IrO …


Proposal For A New Class Of Materials: Spin Gapless Semiconductors, Xiaolin Wang Jan 2008

Proposal For A New Class Of Materials: Spin Gapless Semiconductors, Xiaolin Wang

Australian Institute for Innovative Materials - Papers

The concept of the spin gapless semiconductor in which both electron and hole can be fully spin polarized is proposed, and its possibility is presented on the basis of first-principles electronic structure calculations. Possible new physics and potential applications in spintronic devices based on the spin gapless semiconductors are discussed.


Structure, Ferroelectric Properties, And Magnetic Properties Of The La-Doped Bismuth Ferrite, Zhenxiang Cheng, Aihua Li, Xiaolin Wang, S X. Dou, Kiyoshi Ozawa, Hideo Kimura, S Zhang, Thomas R. Shrout Jan 2008

Structure, Ferroelectric Properties, And Magnetic Properties Of The La-Doped Bismuth Ferrite, Zhenxiang Cheng, Aihua Li, Xiaolin Wang, S X. Dou, Kiyoshi Ozawa, Hideo Kimura, S Zhang, Thomas R. Shrout

Australian Institute for Innovative Materials - Papers

Bi1-xLaxFeO3 ceramics with x=0, 0.1, 0.2, and 0.3 have been synthesized by solid state reaction, starting from metal oxides. A series of structure transformations is found to depend upon the doping level. Below 10% La doping, Bi1-xLaxFeO3 maintains the rhombohedral structure of BiFeO3. However, for Bi0.8La0.2FeO3 and Bi0.7La0.3FeO3, the structures change to the orthorhombic and tetragonal, respectively. La doping significantly reduces electric leakage and leads to successful observation of electrical polarization hysteresis loops. Doping with La also …


Excess Mg Addition Mgb2 /Fe Wires With Enhanced Critical Current Density, Rong Zeng, Lin Lu, Wenxian Li, Jianli Wang, Dongqi Shi, Josip Horvat, S X. Dou, M Bhatia, M D Sumption, Edward W. Collings, Jaimoo Yoo, Mike Tomsic, M Rindfleisch Jan 2008

Excess Mg Addition Mgb2 /Fe Wires With Enhanced Critical Current Density, Rong Zeng, Lin Lu, Wenxian Li, Jianli Wang, Dongqi Shi, Josip Horvat, S X. Dou, M Bhatia, M D Sumption, Edward W. Collings, Jaimoo Yoo, Mike Tomsic, M Rindfleisch

Australian Institute for Innovative Materials - Papers

MgB2 /Fe wires with 10 at. % excess Mg produced by in situ powder-in-tube processing werecompared to normal stoichiometric MgB2 /Fe wires prepared by the same method. It was found thatthe critical current density Jc and the irreversibility field (Hirr) were significantly enhanced forMgB2 /Fe wires with excess Mg. The transport Jc for 10 at. % Mg excess samples sintered at 800 degrees C, measured at a field of up to 14 T, increased by a factor of 2 compared to that for the normal MgB2 wires. The best Jc results …


Optical Property And Electronic Band Structure Of A Piezoelectric Compound Ga3po7 Studied By The First-Principles Calculation, Zhenxiang Cheng, Xiaolin Wang Jan 2008

Optical Property And Electronic Band Structure Of A Piezoelectric Compound Ga3po7 Studied By The First-Principles Calculation, Zhenxiang Cheng, Xiaolin Wang

Australian Institute for Innovative Materials - Papers

The structure, electronic and optical properties of a piezoelectric material, Ga3PO7 were studied by first-principles calculations in the framework of density functional theory. The calculated structure is in agreement with the experimental data. Band structure reveals that Ga3PO7 has a band gap of 3.69 eV. Analysis of partial density of states and Mulliken charge population indicates existence of GaO5 and PO4 anion groups in Ga3PO7. Furthermore, its optical properties, including dielectric constant, absorption, reflectivity, refractive index, and electron loss were calculated and analysed, which show that Ga3 …


Correlation Between Doping Induced Disorder And Superconducting Properties In Carbohydrate Doped Mgb2, Jung Ho Kim, S X. Dou, Sangjun Oh, M Jercinovic, E Babic, T Nakane, Hiroaki Kumakura Jan 2008

Correlation Between Doping Induced Disorder And Superconducting Properties In Carbohydrate Doped Mgb2, Jung Ho Kim, S X. Dou, Sangjun Oh, M Jercinovic, E Babic, T Nakane, Hiroaki Kumakura

Australian Institute for Innovative Materials - Papers

A comprehensive study of the effects of carbohydrate doping on the superconductivity of MgB2 has been conducted. In accordance with the dual reaction model, more carbon substitution is achieved at lower sintering temperature. As the sintering temperature is lowered, lattice disorder is increased. Disorder is an important factor determining the transition temperature for the samples studied in this work, as evidenced from the correlations among the lattice strain, the resistivity, and the transition temperature. It is further shown that the increased critical current density in the high field region can be understood by a recently-proposed percolation model [M. Eisterer …


Improved Ferroelectric Properties In Multiferroic Bifeo3 Thin Films Through La And Nb Codoping, Zhenxiang Cheng, Xiaolin Wang, S X. Dou, Hideo Kimura, Kiyoshi Ozawa Jan 2008

Improved Ferroelectric Properties In Multiferroic Bifeo3 Thin Films Through La And Nb Codoping, Zhenxiang Cheng, Xiaolin Wang, S X. Dou, Hideo Kimura, Kiyoshi Ozawa

Australian Institute for Innovative Materials - Papers

We report the significant improvement of the ferroelectric properties of BiFeO3thin film through control of electrical leakage by Nb doping. A very large remanent electrical polarization value of 80 µC/cm2 was observed in Bi0.8La0.2Nb0.01Fe0.99O3 thin film on Pt/Ti/SiO2/Si substrate. The doping effect of Nb in reducing the movable charge density due to oxygen vacancies in BiFeO3 was confirmed by the dielectric measurements. A very small loss was observed in the Nb and La codoped BiFeO3 thin film. As well as the improvement in the …


Flux-Pinning Mechanism In Silicone-Oil Doped Mgb2: Evidence For Charge-Carrier Mean Free Path Fluctuation Pinning, Shaban R. Ghorbani, Xiaolin Wang, S X. Dou, Sung-Ik Lee, Md S. Hossain Jan 2008

Flux-Pinning Mechanism In Silicone-Oil Doped Mgb2: Evidence For Charge-Carrier Mean Free Path Fluctuation Pinning, Shaban R. Ghorbani, Xiaolin Wang, S X. Dou, Sung-Ik Lee, Md S. Hossain

Australian Institute for Innovative Materials - Papers

Flux-pinning mechanism of MgB2 doped with 10 wt % silicone-oil sintered at low and high temperatures has been investigated by magnetic measurements. The field dependence of the critical current density, jc(B), was analysed within the collective pinning model. A crossover field, Bsb, from the single vortex to the small vortex bundle-pinning regime was observed. For both types of sintered samples, the temperature dependence of Bsb(T) at low temperature is in good agreement with the δl pinning mechanism, i.e., pinning associated with charge-carrier mean free path fluctuation. At temperatures close to the critical …


Dielectric, Magnetic, And Magnetotransport Properties In Sr Doped Two-Dimensional Re2coo4 (Re=Pr,Eu) Compounds, Qiwen Yao, Xiaolin Wang, S X. Dou Jan 2008

Dielectric, Magnetic, And Magnetotransport Properties In Sr Doped Two-Dimensional Re2coo4 (Re=Pr,Eu) Compounds, Qiwen Yao, Xiaolin Wang, S X. Dou

Australian Institute for Innovative Materials - Papers

In this work, we report on the studies of dielectric, magnetic, and magnetotransport properties of Sr doped RE2-xSrxCoO4 (RE=Pr or Eu, x=0.25-1.5). These compounds were systematically studied in terms of structure, magnetic, magnetotransport, and dielectric constant measurements. Rietveld refinement indicated that these compounds crystallized in K2NiF4-type structure with space group I4/mmm. Lattice parameters increase with Sr doping level. The system changes from paramagnetic to ferromagnetic with increasing Sr doping level and finally becomes ferromagnetic with TC of 230 K for Pr0.75Sr1.25CoO4 and …


A Novel Chipless Rfid System Based On Planar Multiresonators For Barcode Replacement, Stevan Preradovic, Isaac Balbin, Nemai Karmakar, Gerry Swiegers Jan 2008

A Novel Chipless Rfid System Based On Planar Multiresonators For Barcode Replacement, Stevan Preradovic, Isaac Balbin, Nemai Karmakar, Gerry Swiegers

Australian Institute for Innovative Materials - Papers

RFID is taking the world by storm but lowering the price of the tag is a necessity in order to completely replace barcode systems with RFID systems. Researchers around the world have been working on chipless RFID systems. In this paper we present a novel chipless RFID system for barcode replacement. The system can be effectively used in conveyor belt applications. It uses spectral signatures to encoded data and hence provide a unique ID for every tagged object. The chipless tag is fully passive and planar.


Electronic Texture Of The Thermoelectric Oxide Na0.75coo2, M -H Julien, C De Vaulx, H Mayaffre, C Berthier, M Horvatic, V Simonet, J Wooldridge, G Balakrishnan, M R. Lees, Dapeng Chen, C T. Lin, P Lejay Jan 2008

Electronic Texture Of The Thermoelectric Oxide Na0.75coo2, M -H Julien, C De Vaulx, H Mayaffre, C Berthier, M Horvatic, V Simonet, J Wooldridge, G Balakrishnan, M R. Lees, Dapeng Chen, C T. Lin, P Lejay

Australian Institute for Innovative Materials - Papers

From 59Co and 23Na NMR, we demonstrate the impact of the Na+ vacancy ordering on the cobalt electronic states in Na0.75CoO2: at long time scales, there is neither a disproportionation into 75 % Co3+ and 25 % Co4+ states, nor a mixed-valence metal with a uniform Co3.25+ state. Instead, the system adopts an intermediate configuration in which 30 % of the lattice sites form an ordered pattern of localized Co3+ states. Above 180 K, an anomalous mobility of specific Na+ sites is found to coexist with this electronic texture, suggesting that the formation of the latter may contribute to stabilizing …


Influence Of Inductance Variation On Performance Of A Permanent Magnet Claw Pole Soft Magnetic Composite Motor, Youguang Guo, Jian Zhu, Zhi Lin, Haiyan Lu, Xiaolin Wang, Jiaxin Chen Jan 2008

Influence Of Inductance Variation On Performance Of A Permanent Magnet Claw Pole Soft Magnetic Composite Motor, Youguang Guo, Jian Zhu, Zhi Lin, Haiyan Lu, Xiaolin Wang, Jiaxin Chen

Australian Institute for Innovative Materials - Papers

Winding inductance is an important parameter in determining the performance of electrical machines, particularly those with large inductance variation. This paper investigates the influence of winding inductance variation on the performance of a three-phase three-stack claw pole permanent magnet motor with soft magnetic composite (SMC) stator by using an improved phase variable model. The winding inductances of the machine are computed by using a modified incremental energy method, based on three-dimensional nonlinear time-stepping magnetic field finite element analyses. The inductance computation and performance simulation are verified by the experimental results of an SMC claw pole motor prototype.


Enhancement Of Ferroelectricity And Ferromagnetism In Rare Earth Element Doped Bifeo3, Zhenxiang Cheng, Xiaolin Wang, S X. Dou, Hideo Kimura, Kiyoshi Ozawa Jan 2008

Enhancement Of Ferroelectricity And Ferromagnetism In Rare Earth Element Doped Bifeo3, Zhenxiang Cheng, Xiaolin Wang, S X. Dou, Hideo Kimura, Kiyoshi Ozawa

Australian Institute for Innovative Materials - Papers

Rare earth element doped BiFeO3 thin films were fabricated using the pulsed laser deposition method and various targets made from different starting Fe2O3 and Fe3O4 iron source materials. The films fabricated using the targets made from Fe3O4 exhibit great enhancement in their ferroelectricity, due to greatly reduced electrical leakage, as well as enhanced magnetization compared to those films deposited using targets from Fe2O3. It is suggested that the Fe2+ ion plays an important role in compensating for the charge imbalance and reducing current leakage, as …


High Field Performance Of Nano-Diamond Doped Mgb2 Superconductor, Arpita Vajpayee, V P. Awana, H Kishan, Anant Narlikar, G L. Bhalla, Xiaolin Wang Jan 2008

High Field Performance Of Nano-Diamond Doped Mgb2 Superconductor, Arpita Vajpayee, V P. Awana, H Kishan, Anant Narlikar, G L. Bhalla, Xiaolin Wang

Australian Institute for Innovative Materials - Papers

The results from magnetotransport and magnetization of nanodiamond doped MgB2-nDx are reported. Superconducting transition temperature (Tc) is not affected significantly by x up to x =0.05 and latter decreases slightly for higher x>0.05. R(T) vs H measurements show higher Tc values under same applied magnetic fields for the nanodiamond added samples, resulting in higher estimated Hc2 values. From the magnetization measurements, it was found that irreversibility field value Hirr for the pristine sample is 7.5 T at 4 K and the same is increased to 13.5 T for 3 wt % …


Magnetic Anisotropy Of Naxcoo2 Single Crystals, Dapeng Chen, Xiaolin Wang, C T Lin, S X. Dou Jan 2008

Magnetic Anisotropy Of Naxcoo2 Single Crystals, Dapeng Chen, Xiaolin Wang, C T Lin, S X. Dou

Australian Institute for Innovative Materials - Papers

We report the magnetic properties of single crystals of NaxCoO2 (x=0.42, 0.82, and 0.87). The magnetic susceptibility measurements revealed considerable anisotropy along H parallel to ab and H parallel to c for the as-grown single crystals. It was found that an antiferromagnetic transition with a Neel temperature T-N=21 K occurred for the x=0.82 sample, and there was a paramagnetic phase for the x=0.87 sample over a wide temperature range from 2 to 300 K, but the sample with x=0.42 shows a monotonic increase of chi with increasing temperature above similar to 100 K. In addition, …