Anomalous re-entrant glassy magnetic phase in LaMn0.5Co0.5O3 single crystals

We report an anomalous re-entrant glassy magnetic phase in (l00) oriented ferromagnetic LaMn0.5Co0.5O3 single crystals. The characterization is fortified with conventional magnetometry, like linear as-well-as non-linear ac susceptibility and specific heat. As the sample is cooled below the ferromagnetic transition temperature, it reenters a glassy magnetic phase whose dynamics have little resemblance with the conventional response. The glassy transition shifts to a higher temperature with increasing frequency of the applied ac field. But it does not respond to the dc biasing or memory experiment. Specific heat as well as non-linear ac susceptibility data also do not relate to the conventional glassy response. Unusually low magnetic entropy indicates the lack of long range magnetic ordering. The results demonstrate that the glassy phase in LaMn0.5Co0.5O3 is not due to any of the known conventional origins. We infer that the competing ferromagnetic and antiferromagnetic interaction due to high B-site disorder is responsible for this anomalous re-entrant glassy phase. (C) 2016 AIP Publishing LLC.

Prussian blue as a single precursor for synthesis of Fe/Fe3C encapsulated N-doped graphitic nanostructures as bi-functional catalysts

We report a unique, single source precursor Prussian blue (iron(III) ferrocyanide (Fe-4(III)Fe-II(CN)(6)](3))) for the synthesis of Fe/Fe3C nanoparticle encapsulated N-doped graphitic layers and bamboo-like graphitic nanotubes. Hollow N-doped graphite (N-HG) nanostructures are obtained when the encapsulated nanostructures are treated with an acid. Both the encapsulated nanostructures and N-HG are shown to be applicable as bi-functional electrocatalysts for oxygen reduction (ORR) and oxygen evolution reactions (OER). The ORR activity is shown to be improved for N-HG and is comparable to commercial Pt/C. On the other hand, encapsulated nanostructures exhibit OER activity with long-term stability comparable to commercial RuO2.

Emergent photophenomena in three dimensional van der Waals heterostructures

We report on the fabrication and observation of emergent opto-electronic phenomena in three dimensional, micron-sized van der Waals heterostructures self-assembled from atomic layers of graphene and hexagonal boron nitride in varying ratios.

Thermo-optic Degradation of Single-Modedness in Active LMA fibers and Simple Compensation Mechanisms

We demonstrate significant thermo-optic degradation of single-modedness in active large mode area fibers due to heat generation in the fiber. We propose and demonstrate through simulations, simple compensation mechanisms using custom length dependent fiber coiling.

Reduced common-mode voltage operation of a new seven-level hybrid multilevel inverter topology with a single DC voltage source

In this study, analysis of extending the linear modulation range of a zero common-mode voltage (CMV) operated n-level inverter by allowing reduced CMV switching is presented. A new hybrid seven-level inverter topology with a single DC supply is also presented in this study and inverter operation for zero and reduced CMV is analysed. Each phase of the inverter is realised by cascading two three-level flying capacitor inverters with a half-bridge module in between. Proposed inverter topology is operated with zero CMV for modulation index <86% and is operated with a CMV magnitude of V-dc/18 to extend the modulation range up to 96%. Experimental results are presented for zero CMV operation and for reduced common voltage operation to extend the linear modulation range. A capacitor voltage balancing algorithm is designed utilising the pole voltage redundancies of the inverter, which works for every sampling instant to correct the capacitor voltage irrespective of load power factor and modulation index. The capacitor voltage balancing algorithm is tested for different modulation indices and for various transient conditions, to validate the proposed topology.

Enhancing photoresponsivity using MoTe2-graphene vertical heterostructures

MoTe2 with a narrow band-gap of similar to 1.1 eV is a promising candidate for optoelectronic applications, especially for the near-infrared photo detection. However, the photo responsivity of few layers MoTe2 is very small (<1mAW(-1)). In this work, we show that a few layer MoTe2-graphene vertical heterostructures have a much larger photo responsivity of similar to 20mAW(-1). The trans-conductance measurements with back gate voltage show on-off ratio of the vertical transistor to be similar to(0.5-1) x 10(5). The rectification nature of the source-drain current with the back gate voltage reveals the presence of a stronger Schottky barrier at the MoTe2-metal contact as compared to the MoTe2-graphene interface. In order to quantify the barrier height, it is essential to measure the work function of a few layers MoTe2, not known so far. We demonstrate a method to determine the work function by measuring the photo-response of the vertical transistor as a function of the Schottky barrier height at the MoTe2-graphene interface tuned by electrolytic top gating. (C) 2016 AIP Publishing LLC.

A noble and single source precursor for the synthesis of metal-rich sulphides embedded in an N-doped carbon framework for highly active OER electrocatalysts

Here, we demonstrate a green and environment-friendly pyrolysis route for the synthesis of metal-rich sulphide embedded in an N-doped carbon (NC) framework in the absence of sulphide ions (S2-). The metal-chelate complex (tris(ethylenediamine) metal(II) sulfate) serves as a new and single source precursor for the synthesis of earth abundant and non-precious hybrid structures such as metal-rich sulphides Co9S8@NC and Ni3S2@ NC when M-II = Co2+ and Ni2+ and counter sulphate (SO42-) ions are the source of S. Both the hybrids show superior OER activity as compared to commercial RuO2.