Rogue waves in multi‐pair plasma medium

The non‐linear propagation of ion acoustic (IA) waves, which is governed by the non‐linear Schrödinger equation, in multi‐pair plasmas (MPPs) containing adiabatic positive and negative ion fluids as well as non‐extensive (q‐distributed) electrons and positrons is theoretically investigated. It is observed that the MPP under consideration supports two types of modes, namely fast and slow IA modes, and the modulationally stable and unstable parametric regimes for the fast and slow IA modes are determined by the sign of the ratio of the dispersive coefficient to the non‐linear one. It is also found that the modulationally unstable regime generates highly energetic IA rogue waves (IARWs), and the amplitude as well as the width of the IARWs decreases with increase in the value of q (for both q > 0 and q < 0 limits). These new striking features of the IARWs are found to be applicable in the space (i.e., D‐region [], and F‐region [H⁺, H^?] of the Earth's ionosphere) and laboratory MPPs (i.e., fullerene [C⁺, C^?]).     

Structural,electronic and magnetic properties of quaternary half‐metallic Heusler alloy CoFeCrAl

We have investigated the structural, electronic and magnetic properties in quaternary CoFeCrAl Heusler alloy. Rietveld refinement and Mössbauer spectroscopy of samples quenched from 973 K show absence of the A2 phase and presence of a highly ordered B2‐type structure. Full‐potential linearized augmented plane wave calculations using the experimental lattice constant show that there is an energy gap of 0.41 eV around the Fermi level in the bands for minority spin electrons. Partial substitution of Co by Fe in Co₂CrAl thus brings excellent structural ordering while retaining the high Curie temperature, spontaneous magnetization and half‐metallicity necessary for application as spin valves. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)