Crystal growth of the Ca2RuO4–Ru metal system by the floating-zone technique

In the last few decades there has been growing interest in studying Mott insulators due to their ability to host novel quantum phenomena when the system is perturbed by various stimuli. Recently the antiferromagnetic Mott insulator Ca2RuO4 has received considerable attention due to superconductivity and metal-insulator transition induced by pressure and electric field respectively. Here we report the details of the synthesis of a novel systems made by Ca2RuO4 and Ru metal inclusions. Samples with lamellae, rods and globules of Ru embedded in Ca2RuO4 single crystals were successfully synthesized by floating zone technique with an excess of Ru in the starting material. The morphology and structural studies revealed a randomly orientated distribution of the shining Ru inclusions with an average size of few microns. Magnetic and electrical properties showed a behavior similar to the one observed in single crystals with the only Ca2RuO4 phase. We also measured the current-voltage characteristics of the whole Ca2RuO4–Ru system and of a single Ru rod by electric micro-contacts estimating the room temperature resistivity of the Ru embedded inclusions. This study shows that physical properties of Ca2RuO4–Ru metal system are related to the properties of the constituent phases, similarly to the case of Sr2RuO4–Ru metal.