The half-Heusler intermetallic ferromagnet CoMSb (M = V, Cr, and Mn) is theoretically predicted to realize large anomalous Nernst effect. We successfully synthesized single crystals of CoMnSb, which has the highest Curie temperature of 490 K in the CoMSb enough for Nernst type thermoelectric device to be applicable at room temperature. The powder X-ray diffraction measurements show that the obtained crystals have the 2 × 2 × 2 superlattice structure (= 11.835 Å) of half-Heusler CoMnSb (= 5.875 Å). The observed magnetization saturated around 4 B /f.u., which also indicates that the obtained CoMnSb crystals have the superlattice structure.
We report a synthesis route to form a stable powder of SrCoO3-δ which show ferromagnetic component at room temperature. The powder was obtained from brownmillerite SrCoO2.5 using chemical oxidation. The x-ray diffraction pattern of the oxidized powder was best fitted using a tetragonal structure of I4/mmm with lattice constants of a = b = 10.87 Å, c = 7.664 Å and its oxygen content of 2.77 (δ 0.23) was measure by iodometric titration. In spite of a single-phase structure, the elemental compositions of oxidized powder characterized by the EDX measurement showed the presence of oxidation elements that might contribute to magnetic impurities at low temperatures. The powder nevertheless can be used for magnetic applications at room temperature.
We investigated the stability of the high-spin state of the iron β-NaFeO2 based on the structural refinement. The oxidation of the Fe2+ ion in the as-synthesized sample is evidenced by its green color. Due to its sensitivity in air and CO2, this compound will decompose into a reddish Fe3+ state. The smaller crystal volume of the decomposed compound is mainly related to the shorter ionic radius of the high-spin state Fe3+ and this result will be compared to the single crystal sample. In contrast to the polycrystalline sample, the decomposition single crystal sample only taking place on the surface of the as-grown crystal.
Crystal structure and magnetic properties of Heusler-alloy Co2MnGa were examined systematically using non-stoichiometric compositions of Co and Mn element from the Czochralski as-grown single crystal samples. The crystalline structure of each sample was characterized by means of X-ray powder diffraction technique. Each sample was treated with and without heat treatment at 923 K for 10 hours. The effects of Co and Mn excess were observed in the lattice constants for both treatments. The L21-type crystal structure was observed only for the heat-treated samples. The changes in lattice constants are attributed to the substitution of atomic sites. The excess of Co tends to decrease the crystal volume, in opposite to the excess of Mn. In order to investigate the Slater-Pauling rule in the non-stoichiometric samples, the saturation magnetic moments were measured from the field-dependent magnetization measurement for the as-grown samples at 2 K. The deviation from the Slater-Pauling rule was found in the lower concentration of valence electron which associated to the lower total fraction of both Co and Mn. This indicates that the magnetic interactions of these materials cannot only be contributed to the number of valence electron.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.