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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)

A series of cobalt ferrite samples were synthesized from a metal nitrate solution at constant pH between 9 and 12 by the controlled co-precipitation method without any surfactant. Cobalt and iron nitrates and sodium hydroxide base were simultaneously dosed so that the pH was precisely controlled during co-precipitation. The samples were characterized by PXRD, SEM, TEM, BET, and TPR. Careful analysis of typical PXRD peak profiles suggested the presence of two different variants of cobalt ferrite, a nano-scale material giving rise to broad peak tails and a more crystalline material leading to a sharper central profile. Rietveld refinement could be used to quantify the relative amount of both nano and crystalline fractions in these samples indicating that their relative abundance can be controlled by the co-precipitation pH. TEM analysis further proved the presence of both crystalline and nanocrystalline region in the samples. The average crystallite size of the cobalt ferrite nanocrystallites was 4–5 nm. These samples exhibit high BET surface area, in the order of 200 m2 g^-1. The samples were tested for catalytic performance in the CO oxidation reaction. The surface area, reduction behavior, and catalytic performance of ferrites were dependent on the relative amount of both the crystalline and nanocrystalline phases

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