Physics Commons^™

Revisiting Galvanomagnetic Effects In Conducting Ferromagnets, Raymond T. Walter, Michel Viret, Surendra Singh, Laurent Bellaiche

Raymond Walter

Rhodizonic Acid On Noble Metals: Surface Reactivity And Coordination Chemistry, Donna A. Kunkel, James Hooper, Scott Simpson, Sumit Beniwal, Katie L. Morrow, Douglas C. Smith, Kimberly Cousins, Stephen Ducharme, Eva Zurek, Axel Enders

Axel Enders

A study of the two-dimensional crystallization of rhodizonic acid on the crystalline surfaces of gold and copper is presented. Rhodizonic acid, a cyclic oxocarbon related to the ferroelectric croconic acid and the antiferroelectric squaric acid, has not been synthesized in bulk crystalline form yet. Capitalizing on surface-assisted molecular self-assembly, a two-dimensional analogue to the well-known solution-based coordination chemistry, two-dimensional structures of rhodizonic acid were stabilized under ultrahigh vacuum on Au(111) and Cu(111) surfaces. Scanning tunneling microscopy, coupled with first-principles calculations, reveals that on the less reactive Au surface, extended two-dimensional islands of rhodizonic acid are formed, in which the molecules …

Ferromagnetic Granular Exchange Interactions Of Nickel And Iron, Ken Podolak

Dr. Ken Podolak

Micromagnetic grains of nickel and iron were blended to investigate whether the magnetic exchange interaction was significant to produce a bulk result in a measured deflection by a fixed applied magnetic field. The results follow the same trend as Slater-Pauling's magnetization density calculations for nickel iron films, most notably a stronger following with a finer grain. Furthermore, by adding chromium into nickel and iron blends, the Invar minimum shifts toward less iron in nickel. Hysteresis was determined for the same samples through a homemade vibrating sample magnetometer (VSM). Areas of each loop are determined that show a minimum around the …

Investigation Of Carrier Transit Motion In Pcdtbt By Optical Shg Technique, Shahino Mah Abdullah

Shahino Mah Abdullah

We analyze the carrier transit behavior in poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT), which has been reported as a donor material for efficient bulk hetero junction photovolatic devices. The transfer and transient carrier mobilities in the PCDTBT thin films have been measured and analyzed. The transfer mobility has been measured by the transfer curve of the OFET, whereas, the transient mobility is recorded using a time-resolved electric-field-induced optical second-harmonic-generation (TRM-SHG) technique. Using TRM-SHG technique, the dynamic motion of the charge carriers in the PCDTBT thin films has been directly visualized. We anticipate that the analysis of the carrier motion by TRM-SHG, will be effective …

The Jahn–Teller Effect And Electron–Phonon Interaction In La0.25ca0.75mn1−Xcrxo3, H. Zhou, G. Li, H. Chen, R. Zheng, Xiaojuan Fan, X. Li

Xiaojuan Fan

The ultrasonic (longitudinal and transverse) velocities and the transport and magnetic properties of polycrystalline La0.25Ca0.75Mn1-xCrxO3 (x = 0, 0.03, 0.05, and 0.07) have been studied systematically. It was found that with increasing Cr content, the resistivity increases, the charge-ordering transition temperature TCO shifts to low temperature, and the magnetic moment of the system is strengthened. From the temperature dependence of the ultrasonic velocities, one can establish that the Jahn-Teller energy and phonon exchange constant decrease with increasing Cr content.

Investigation Of Charge Transport In Organic Polymer Donor/Acceptor Photovolatic Materials, Zubair Ahmad, Shahino Mah Abdullah, Khaulah Sulaiman

Zubair Ahmad

Pi-conjugated organic semiconductors have long been used as either holes or electrons transport materials. Recently ambipolar charge carrier transport in these materials have been reported in many investigations. In this paper, we report on the basis of experimental results that the organic semiconductor (donor/acceptor) materials can be as good electrons transporters as these materials are holes transporters. In our study, the solution-processed unipolar diodes based on organic materials P3HT, VOPCPhO and their blends with PCBM have been fabricated. The I-V characteristics of these diodes have been analyzed in the space charge limited current regime. The values of the electron and …

Spin Transfer Of Quantum Information Between Majorana Modes And A Resonator, Alexey Kovalev

Alexey Kovalev

No abstract provided.

Absorption Of Microwaves In La1Àxsrxmno3 Manganese Powders Over A Wide Bandwidth, G. Li, G. G. Hu, H. D. Zhou, Xiaojuan Fan, X. G. Li

Xiaojuan Fan

We present the frequency dependence of microwave-absorbing properties of La_1-xSr_xMnO₃ (x=0.4, 0.5, 0.6, and 0.7) powders at room temperature. The absorbing properties change gradually with x in the frequency range of 8–12 GHz. The optimal absorption can be achieved for a x=0.4 sample and its microwave loss peak value is about 25 dB. Further experimental results show that the absorption can be attributed to magnetic and dielectric losses and the microwave loss peak corresponds to the maximum dielectric loss tangent tan δ_e near 10.5 GHz. Furthermore, the absorbing properties of the oxides mixed with …

Competition Between Ferromagnetic Metallic And Paramagnetic Insulating Phases In Manganites, G. Li, H. Zhou, S. Feng, Xiaojuan Fan, X. Li, Z. Wang

Xiaojuan Fan

La0.67Ca0.33Mn1−xCuxO3(x=0 and 0.15) epitaxial thin films were grown on the (100) LaAlO3 substrates, and the temperature dependence of their resistivity was measured in magnetic fields up to 12 T by a four-probe technique. We found that the competition between the ferromagnetic metallic (FM) and paramagnetic insulating (PI) phases plays an important role in the observed colossal magnetoresistance(CMR) effect. Based on a scenario that the doped manganites approximately consist of phase-separated FM and PI regions, a simple phenomenological model was proposed to describe the CMR effect. Using this model, we calculated the resistivity as functions of temperature and magnetic field. The …

Transport Evidence Of Robust Topological Surface State In Bitecl Single Crystals, The First Strong Inversion Asymmetric Topological Insulator, F Xiang

F X Xiang

Three-dimensional (3D) topological insulators (TIs) are new forms of quantum matter that are characterized by their insulating bulk state and exotic metallic surface state, which hosts helical Dirac fermions1-2. Very recently, BiTeCl, one of the polar semiconductors, has been discovered by angle-resolved photoemission spectroscopy to be the first strong inversion asymmetric topological insulator (SIATI). In contrast to the previously discovered 3D TIs with inversion symmetry, the SIATI are expected to exhibit novel topological phenomena, including crystalline-surface-dependent topological surface states, intrinsic topological p-n junctions, and pyroelectric and topological magneto-electric effects3. Here, we report the first transport evidence for the robust topological …

Bulk Fermi Surface And Momentum Density In Heavily Doped La₂₋ₓsrₓcuo₄ Using High-Resolution Compton Scattering And Positron Annihilation Spectroscopies, W. Al-Sawai, B. Barbiellini, Y. Sakurai, M. Itou, P. E. Mijnarends, R. S. Markiewicz, S. Kaprzyk, S. Wakimoto, M. Fujita, S. Basak, H. Lin, Yung Jui Wang, S. W. H. Eijt, H. Schut, K. Yamada, A. Bansil

Hsin Lin

We have observed the bulk Fermi surface (FS) in an overdoped (x=0.3) single crystal of La₂₋ₓSrₓCuO₄ by using Compton scattering. A two-dimensional (2D) momentum density reconstruction from measured Compton profiles yields a clear FS signature in the third Brillouin zone along [100]. The quantitative agreement between density functional theory (DFT) calculations and momentum density experiment suggests that Fermi-liquid physics is restored in the overdoped regime. In particular the predicted FS topology is found to be in good accord with the corresponding experimental data. We find similar quantitative agreement between the measured 2D angular correlation of positron annihilation radiation (2D-ACAR) spectra …

Fermi-Surface Topology And Low-Lying Electronic Structure Of The Iron-Based Superconductor Ca₁₀(Pt₃As₈)(Fe₂As₂)₅, Madhab Neupane, Chang Liu, Su-Yang Xu, Yung-Jui Wang, Ni Ni, J. Allred, N. Alidoust, Hsin Lin, R. Markiewicz, A. Bansil, R. Cava, M. Hasan

Hsin Lin

We report a study of low-energy electronic structure and Fermi surface topology for the recently discovered iron-based superconductor Ca₁₀(Pt₃As₈)(Fe₂As₂)₅(the 10-3-8 phase, with Tc∼8 K), via angle-resolved photoemission spectroscopy (ARPES). Despite its triclinic crystal structure, ARPES results reveal a fourfold symmetric band structure with the absence of Dirac-cone-like Fermi dots (related to magnetism) found around the Brillouin zone corners in other iron-based superconductors. Considering that the triclinic lattice and structural supercell arise from the Pt₃As₈ intermediary layers, these results indicate that those layers couple only weakly to the FeAs layers in this new superconductor at least near the surface, which has …

X-Ray Structure, Thermodynamics, Elastic Properties And Mdsimulations Of Cardiolipin/Dimyristoylphosphatidylcholine Mixedmembranes, Alex Boscia, Bradley Treece, Dariush Mohammadyani, Judith Klein-Seetharaman, Anthony Braun, Beate Kloesgen, Tsjerk Wassenaar, Stephanie Tristram-Nagle

Prof. Stephanie Tristram-Nagle Ph.D.

tCardiolipins (CLs) are important biologically for their unique role in biomembranes that couple phos-phorylation and electron transport like bacterial plasma membranes, chromatophores, chloroplasts andmitochondria. CLs are often tightly coupled to proteins involved in oxidative phosphorylation. The firststep in understanding the interaction of CL with proteins is to obtain the pure CL structure, and the struc-ture of mixtures of CL with other lipids. In this work we use a variety of techniques to characterize the fluidphase structure, material properties and thermodynamics of mixtures of dimyristoylphosphatidylcholine(DMPC) with tetramyristoylcardiolipin (TMCL), both with 14-carbon chains, at several mole percentages.X-ray diffuse scattering was used to …

Shaping Carbon Nanotube Forests For Field Emission, Ben Pound

Ben Pound

No abstract provided.