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Abstract: The LiFeAs superconductor is studied by 57Fe Mössbauer spectroscopy to detect possible changes in the hyperfine parameters in terms of temperature upon passing the superconductivity-transition-temperature at ∼16 K. With decreasing temperature, a rather fast growth of spectral area and isomer shift below , peaking at ∼6 K was seen. This indicates an increase in the stiffness of the lattice followed by softening. [Copyright &y& Elsevier]

Abstract: First principles calculations have been performed to study the electronic structure and the ferromagnetic properties on the two chain compounds of [M(N3)2(HCOO)][(CH3)2NH2] (M=Fe and Co). The relative stability of the ground state, the density of states and the electronic band structure are examined. The results reveal that antiferromagnetism (AFM) state is the ground state and ferromagnetism (FM) state is the metastable one for both of them. The two compounds exhibit semiconductor character with small gap in the FM state, while metallic in the AFM state. In the FM state, the magnetic moments mainly arise from the Fe and Co ions with little contribution from the nearest-neighboring N and O atoms due to the hybridization between the Fe or Co 3d states and the nearest-neighboring N and O 2p states. [Copyright &y& Elsevier]