Critical Slowing Down Along the Dynamic Phase Boundary in Ising Meanfield Dynamics

We studied the dynamical phase transition in kinetic Ising ferromagnets driven by oscillating magnetic field in meanfield approximation. The meanfield differential equation was solved by sixth order Runge-Kutta-Felberg method. The time averaged magnetisation plays the role of the dynamic order parameter. We studied the relaxation behaviour of the dynamic order parameter close to the transition temperature, which depends on the amplitude of the applied magnetic field. We observed the critical slowing down along the dynamic phase boundary. We proposed a power law divergence of the relaxation time and estimated the exponent. We also found its dependence on the field amplitude and compared the result with the exact value in limiting case.Comment: 6 pages Latex, 5 figure

Origin of magnetic moments and presence of a resonating valence bond state in Ba2_2YIrO6_6

While it was speculated that 5$d^4$ systems would possess non-magnetic $J$~=~0 ground state due to strong Spin-Orbit Coupling (SOC), all such systems have invariably shown presence of magnetic moments so far. A puzzling case is that of Ba$_2$YIrO$_6$, which in spite of having a perfectly cubic structure with largely separated Ir$^{5+}$ ($d^4$) ions, has consistently shown presence of weak magnetic moments. Moreover, we clearly show from Muon Spin Relaxation ($\mu$SR) measurements that a change in the magnetic environment of the implanted muons in Ba$_2$YIrO$_6$ occurs as temperature is lowered below 10~K. This observation becomes counterintuitive, as the estimated value of SOC obtained by fitting the RIXS spectrum of Ba$_2$YIrO$_6$ with an atomic $j-j$ model is found to be as high as 0.39~eV, meaning that the system within this model is neither expected to possess moments nor exhibit temperature dependent magnetic response. Therefore we argue that the atomic $j-j$ coupling description is not sufficient to explain the ground state of such systems, where despite having strong SOC, presence of hopping triggers delocalisation of holes, resulting in spontaneous generation of magnetic moments. Our theoretical calculations further indicate that these moments favour formation of spin-orbital singlets in the case of Ba$_2$YIrO$_6$, which is manifested in $\mu$SR experiments measured down to 60~mK.Comment: 20 Pages, 7 Figure

Swarms of ctenophore Pleurobrachia pileus (O. F. Müller, 1776) in the waters of Sundarban: A menace to the fisheries?

1089-1092An unusual swarm of Pleurobrachia pileus (O. F. Müller, 1776) was recorded in the Sundarban coastal waters of Bay of Bengal, Northern Indian Ocean during the winter monsoon season of 2018. The species occurred in the Sundarban waters with an average abundance of 6,766 individual m-3 which in turn diminished the population of other zooplankton and fish. The hydrographical characters observed in the swarm stations favoured the proliferation of Pleurobrachia pileus and the unique factors were low temperature (18.9 – 20.9 °C), high salinity (~24 psu) and associated high biological production. The phenomenon of P. pileus swarm has not been reported earlier from the coastal waters of Sundarban, therefore, our incidental observation provides further insight to explore the study area

Origin of the Spin-Orbital Liquid State in a Nearly J=0 Iridate Ba3ZnIr2O9

We show using detailed magnetic and thermodynamic studies and theoretical calculations that the ground state of Ba3ZnIr2O9 is a realization of a novel spin-orbital liquid state. Our results reveal that Ba3ZnIr2O9 with Ir5+ (5d(4)) ions and strong spin-orbit coupling (SOC) arrives very close to the elusive J = 0 state but each Ir ion still possesses a weak moment. Ab initio density functional calculations indicate that this moment is developed due to superexchange, mediated by a strong intradimer hopping mechanism. While the Ir spins within the structural Ir2O9 dimer are expected to form a spin-orbit singlet state (SOS) with no resultant moment, substantial frustration arising from interdimer exchange interactions induce quantum fluctuations in these possible SOS states favoring a spin-orbital liquid phase down to at least 100 mK

Intercropping System of Maize with Different Winter Vegetables

The experiment was conducted at farmers’ fields of Hqripur in Dauadkandiupzilla underOn- Farm Research Division of Bangladesh Agricultural Research Institute, Comilla during the rabi seasons of 2012-13 and 2013-14 toevaluate the performance of maizeunder intercropping with different winter vegetables. The experiment comprised of four treatments viz., Maize + Spinach, Maize + Red amaranth, Maize + Coriander and Sole maize with four replications. Results revealed that each of maize- vegetables intercropping combinations showed superior in terms of gross return,net return, BCR and Maize equivalent yield (MEY) over sole cropping of maize. The highest grain yield of maize (9.61 t ha-1) was obtained fromMaize + coriander due to the highest contribution of yield contributing characters and lowest (7.8 t ha-1) yield was received from the treatment of maize + red amaranth intercropping system, where the sole maize produced second highest yield.The highest Maize equivalent yield (12.85 t ha-1), gross return (Tk. 128500 ha-1), net return (Tk. 80080 ha-1) and BCR (2.65) were found in the intercropping system Maize + Spinach which indicated the advantage of intercropping over the sole Maize cropping. &nbsp