Istituto dei materiali per l'elettronica ed il magnetismo     
Martinelli A., Ferretti M., Manfrinetti P., Palenzona A., Tropeano M., Cimberle M. R., Ferdeghini C., Valle R., Bernini C., Putti M., Siri A. S. Synthesis, crystal structure, microstructure, transport and magnetic properties of SmFeAsO and SmFeAs(O0.93F0.07). In: Superconductor Science & Technology, vol. 21 (9) article n. 095017. IOP Publishing Ltd, 2008.
SmFeAsO and the isostructural superconducting SmFeAs(O0.93F0.07) phase were prepared and characterized by means of Rietveld refinement of x-ray powder diffraction data, scanning electron microscope observation, transmission electron microscope analysis, and resistivity and magnetization measurements. Sintering treatment strongly improves the grain connectivity, but, on the other hand, induces a competition between the thermodynamic stability of the oxy-pnictide and Sm2O3, thus affecting the sample purity. In the pristine sample both magnetization and resistivity measurements clearly indicate that two different sources of magnetism are present: the former related to Fe ordering at T ∼ 140 K and the latter due to the Sm ions that order antiferromagnetically at low temperature. The feature at 140 K disappears in the F-substituted sample, and a superconducting transition appears, at low temperatures. The magnetoresistivity curves of the F-substituted sample probably indicate very high critical field values
DOI: 10.1088/0953-2048/21/9/095017
Subject Superconductivity

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