Influence of Sample Preparation Technology and Treatment on Magnetism and Superconductivity of UCoGe

概要

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Ferromagnetic superconductor UCoGe is reported to be a week ferromagnet with Curie phase transition temperature T_{\text{C}} \approx 2.5 K. The magnetic order coexists with superconductivity that appears below critical temperature T_{\text{SC}} \approx 0.7 K. Nevertheless, the exotic coexistence of the mentioned physical phenomena is strongly sample dependent and only few samples can take pride in thereby. We have prepared a series of polycrystalline samples and single crystals using Czochralski and floating zone method. The samples were treated by a standard annealing under the vacuum or refined using solid state electrotransport. All samples were carefully characterized by X-ray and neutron diffraction methods and by electron-dispersive X-ray analysis in a scanning electron microscope. They were subsequently also studied with respect to magnetism and superconductivity by electrical resistivity, magnetization, AC susceptibility and specific heat measurements. The results have been analyzed and the relations between the sample quality, ferromagnetism and superconductivity are discussed.
2011-08-15