Department of Physics

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IIT Jodhpur

Unambiguous evidence for the engagement of CF3 group in N-H···F-C hydrogen bond in a low polarity solvent, the first observation of its kind, is reported. The presence of such weak molecular interactions in the solution state is convincingly established by one and two-dimensional 1H, 19F, and natural abundant 15N NMR spectroscopic studies. The strong and direct evidence is derived by the observation of through-space couplings, such as, 1hJFH, 1hJFN, and 2hJFF, where the spin polarization is transmitted through hydrogen bond. In an interesting example of a molecule containing two CF 3 groups getting simultaneously involved in hydrogen bond, where hydrogen bond mediated couplings are not reflected in the NMR spectrum, 19F-19F NOESY experiment yielded confirmatory evidence. Significant deviations in the strengths of 1JNH, variable temperature, and the solvent induced perturbations yielded additional support. The NMR results are corroborated by both DFT calculations and MD simulations, where the quantitative information on different ways of involvement of fluorine in two and three centered hydrogen bonds, their percentage of occurrences, and geometries have been obtained. The hydrogen bond interaction energies have also been calculated. © 2013 American Chemical Society.

World University root node

Journal of Physical Chemistry B

Engagement of CF3 group in N-H···F-C hydrogen bond in the solution state: NMR spectroscopy and MD simulation studies

We investigate the dynamics of two-photon correlations generated by the interaction of a three-level atom in the Ξ, Λ or V configuration, with two classical external driving fields, under the rotating-wave approximation, in the presence of level decays. Using the example of a rubidium atom in each configuration, with field strengths validating the single-photon approximation, we compute measurement-based correlations, such as measurement induced disturbance (MID), quantum discord (QD), and quantum work deficit (WD), and compare the results with that from quantum entanglement (concurrence). Certain correlation properties observed are generic, model independent and consistent with known results, e.g.,MID is an upper bound on QD, QD and WD are monotonic, and the generic correlation behavior is strongly affected by the purity of the photon states. We observe that the qualitative hierarchy, monotonicity and steady-state behavior of the correlations can be controlled through the choice of parameters such as atomic decay constants and external driving field strengths. We point out how particular configurations are better suited to generating monotonic correlations in specific regimes and how the steady-state correlation behavior and hierarchy are affected by the population dynamics of the density matrix for different parameters. The possibility of using well studied quantum optical systems such as the three-level atom to generate, characterize and parametrically control mixed state quantum correlations establishes an important step in the direction of their implementation in quantum information tasks. © 2013 Elsevier Inc.

Fulltext

Annals of Physics

Controllable quantum correlations of two-photon states generated using classically driven three-level atoms

In this paper, a small novel octagonal shaped ultra wideband (UWB) antenna was designed using Minkowski like fractal geometry including the multi band notch characteristics. The investigated UWB antenna geometry addresses the challenges such as compact size and wideband operating frequency range because of the self-similar and multiple resonance characteristics of the fractal geometry, used in this work. The multiple notches in the ground plane leads to better return loss and the desired operational bandwidth in the 3.1 GHz - 10.6 GHz range. The compact 16.5 mm × 13.5 mm antenna geometry exhibits nearly omnidirectional radiation pattern, proper impedance matching with VSWR &lt; 2 over the entire UWB frequency range. These characteristics offer opportunities to explore the proposed UWB antenna for various applications. © 2013 IEEE.

Department of Mathematics

2013 International Conference on Signal Processing and Communication, ICSC 2013

A novel multi band notched octagonal shaped fractal UWB antenna

We demonstrate that a single brain-neuron-extracted microtubule is a memory-switching element, whose hysteresis loss is nearly zero. Our study shows how a memory-state forms in the nanowire and how its protein arrangement symmetry is related to the conducting-state written in the device, thus, enabling it to store and process ∼500 distinct bits, with 2 pA resolution between 1 nA and 1 pA. Its random access memory is an analogue of flash memory switch used in a computer chip. Using scanning tunneling microscope imaging, we demonstrate how single proteins behave inside the nanowire when this 3.5 billion years old nanowire processes memory-bits. © 2013 American Institute of Physics.

Applied Physics Letters

Multi-level memory-switching properties of a single brain microtubule

Ni55Mn22Ga23-xAlx (0 ≤ x ≤ 5) melt spun ribbons homogenized at 1073 K for 30 h exhibited an elevation in martensitic transformation onsets and a reduction in Curie temperature with increase in Al content. The phenomenon has been attributed to different site occupancy by Al, exchange coupling and paramagnetic martensite during thermal and magnetic transitions. Transmission Electron microscopy revealed systematic patterns of dislocations in alloy with x = 1, which become denser at high Al content. X = 1 alloy revealed high magnetic field induced strain (MFIS) value it is attributed to a critical combination of austenite and martensite phase. © 2013 Elsevier B.V. All rights reserved.

Intermetallics

Martensitic transformation and magneto-strain in melt spun NiMnGaAl Ferromagnetic Shape Memory Alloys

We report here a facile chemical method to prepare ZnO nanorods with micrometer length in large quantity at 80 °C. The as-prepared rods exhibited blue emission and room temperature ferromagnetism simultaneously. The PL of the as-prepared ZnO rods exhibited an overlapped broad emission in the 345-600 nm range. The as-prepared dried rods exhibited a saturation magnetization value of 59.14 × 10-3 emu g-1 at room temperature. On heating, though the material retains its morphology, the magnetization value decreased. Since we have observed a reduction in the intensity of the visible emission followed by a disappearance of the ferromagnetic ordering, we attributed the blue emission and the ferromagnetism to the presence of defects related to singly ionized oxygen vacancies and zinc vacancies. © 2013 Elsevier B.V. All rights reserved.

Materials Chemistry and Physics

Synthesis of blue emitting ZnO nanorods exhibiting room temperature ferromagnetism

Rapidly quenched bilayered ribbons comprising one layer as Fe 73.5Nb3Cu1Si13.5B9 (FM) and the other layer either as Fe74.5Nb3Si 13.5B9 (FNb) or Co72.5Si12.5B 15 (CSB) alloy designated as BLFM/FNb and BL FM/CSB, respectively, have been addressed. Phase transformation, thermomagnetic transitions, saturation magnetization, and soft magnetic properties of individual layers were revealed in the functional properties of bilayered ribbons. Properties of bilayer could be endorsed with respect to the single layered Fe73.5Nb3Cu1Si 13.5B9, Fe74.5Nb3Si 13.5B9, and Co72.5Si12.5B 15 alloy ribbons. Selective devitrification of the layers in the bilayers could be induced through optimum heat treatment. Enhanced bend sensitivity was revealed in BLFM/CSB through generation of desirable phases in the bilayers of the bilayered ribbon. Synergistic diffusivity of Fe and Co with its consequent effect on interfacial zone of BLFM/CSB bilayer was observed. © 2013 AIP Publishing LLC.

Journal of Applied Physics

Functional gradation through preferential crystallisation and interfacial activity in rapidly quenched Fe/Co-based bilayered ribbons for bend sensors

We report on anomalies in the dielectric and optical phonon spectra in bulk orthorhombic distorted perovskite LaCrO3 near an antiferromagnetic transition at 290 K. These anomalies were tracked using temperature dependent (200 K-320 K) dielectric and Raman spectroscopy. We observed a blue-shift for the B3g(3) optical phonon mode coincident with the onset of antiferromagnetic ordering of LaCrO3 in conjunction with a broad dielectric anomaly near the Néel temperature. The dielectric and optical phonon anomalies are discussed in the context of the observed antiferromagnetic transition in temperature dependent magnetic studies. © 2013 AIP Publishing LLC.

Dielectric and optical phonon anomalies near antiferromagnetic ordering in LaCrO3: A possible near room temperature magnetodielectric system

We report on the structural and magnetic properties of In 2Ga2Fe2O9 and Sc2Ga 2Fe2O9. X-ray diffraction measurements confirmed the presence of a single orthorhombic phase, corresponding to the expected structure for M2Ga2Fe2O9 (M=In, Sc). Neutron diffraction measurements show considerable cation disorder at different lattice sites, and suggest that there is no long range magnetic ordering down to T=10 K. Temperature dependent magnetization measurements show a separation between field-cooled and zero-field-cooled curves near T f≈19 K. Below this temperature the M(H) curves also exhibit history dependent behavior. The temperature dependent ac susceptibility shows a peak in the magnetic dissipation, with the temperature of the peak varying systematically with frequency suggesting that this feature may be associated with a glassy relaxation. Zero-field specific heat measurements down to 4 K do not reveal any long range magnetic ordering of these compounds, nor is there any transition to an ordered state under the application of a 7 T field. © 2012 Elsevier Inc. All rights reserved.

Journal of Solid State Chemistry

Structural and magnetic properties of the M2Ga 2Fe2O9 (M=In, Sc) oxides

We study the impact of decoherence on B meson systems with specific emphasis on Bs. For consistency we also study the Bd mesons based on the most recent data. Even though the study of decoherence made here depends upon the basis chosen and the final decay products, our analysis suggests that the coherence property of B meson systems is robust and could be a good candidate for making a study of foundational aspects of quantum mechanics. © 2013 American Physical Society.