Single-Crystal Growth of Sr2RuO4 by the Floating-Zone Method Using an Infrared Image Furnace with Improved Halogen Lamps

Abstract

We report the single-crystal growth of the unconventional superconductor Sr2RuO4, on which research has reached a turning point recently. In order to optimize the quality of crystals grown by the floating-zone method using an infrared image furnace, we focus on an improvement of the structure of the filament in the halogen lamps. By reducing the thickness of the total filament, the form of the molten zone was narrowed. More importantly, the molten zone was observed to be more stable during the growth process. Finally, we obtained the crystals with a length of 12 cm. Additionally, the grown crystal has high quality, displaying the 1.5 K transition temperature expected only for the purest crystals. We also discuss the availability of the newly developed halogen lamps.

Recent Progress of Floating-Zone Techniques for Bulk Single-Crystal Growth

“…Interestingly, the stability can be evaluated by directly measuring the ratio between the minimum melting width at the zone and the diameter of the grown silicon crystal. This section is closed by briefly tracking a "developing history" of how the molten zone becomes more stable by "downsizing" the filament sizes throughout the crystal growth of a layered perovskite ruthenate, Sr2RuO4 [108,109]. Keeping the molten zone stable is generally hard for ruthenates because of its low viscosity [30][31][32]36,105,[108][109][110][111].…”

“…We This section is closed by briefly tracking a "developing history" of how the molten zone becomes more stable by "downsizing" the filament sizes throughout the crystal growth of a layered perovskite ruthenate, Sr 2 RuO 4 [108,109]. Keeping the molten zone stable is generally hard for ruthenates because of its low viscosity [30][31][32]36,105,[108][109][110][111]. The first generation of the halogen lamp of the ruthenate growth had a "spiral" shaped filament as shown in Figure 12a.…”

“…also noted that the required generating power to form the liquid zone of ruthenates over 2000 °C was still only 80% against fully available power. Finally, the molten zone was reduced to 5 mm (Figure 13c) and a stable molten zone was kept during the entire growth process, as the grown crystal had a 12 cm length with high quality, compared with the 7 cm length obtained using the second-generation filament [109].…”