High-quality single crystal growth of UGe2 and URhGe

We searched for an experimental condition of crystal growth for a ferromagnetic superconductors of UGe2 and URhGe. Samples were prepared for both polycrystalline and single crystals, which were arc-melted and grown by the Czochralski-pulling method in a tetra-arc furnace, respectively. Annealing is an important process to enhance sample-quality, namely the residual resistivity ratio. We tried to anneal the samples under various temperatures, which were wrapped by the Ta-foil and vacuum-sealed in the quartz ample, together with the solid state electrotransport method in ultra-high vacuum. The highest residual resistivity ratio was 900 for UGe2 and 41 for URhGe. (C) 2003 Published by Elsevier B.V.