Single-Crystal Growth of a Cubic Laves-Phase Ferromagnet HoAl2 by a Laser Floating-Zone Method

Abstract

The successful growth of single crystals of a cubic Laves-phase material HoAl2 with the space group Fd-3m is reported in this study. The crystals were grown by a floating-zone method with five laser diodes as a heat source. Al-rich feed rods were prepared as compensation for heavy evaporation during the growth. The nominal ratio for the feed rods was optimized as Ho:Al = 1:2.5. Single crystals of HoAl2 with a length of 50 mm were first grown in this technique. Obtaining the large-sized crystal by the floating-zone method enabled us to systematically explore the physical properties using the same batch crystal. The crystal possessed a second-ordered ferromagnetic transition at 29 K and a first-ordered spin-reorientation transition at 20 K. The bulk physical properties, such as specific heat, magnetic susceptibility, isothermal magnetization, and thermal expansion measurements, were measured. Additionally, a magnetocaloric effect was evaluated by the magnetic entropy change. We demonstrate that anisotropic physical properties along the principal axes ([100], [110], and [111]) emerged below the magnetically ordered states, in contrast to the isotropic behavior in the paramagnetic state.

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

“…As shown in Figure 16, a multiferroic oxide TbMnO 3 crystal has significant cracks under an unmodified "flat" profile; however, little cracks in the grown crystal are seen when the "modified bell-shape profile" is adopted [113]. Introducing modern laser technology to the floating-zone furnace enabled us to succeed in the crystal growth of quantum materials [117,118].…”

“…As shown in Figure 16, a multiferroic oxide TbMnO3 crystal has significant cracks under an unmodified "flat" profile; however, little cracks in the grown crystal are seen when the "modified bell-shape profile" is adopted [113]. Introducing modern laser technology to the floating-zone furnace enabled us to succeed in the crystal growth of quantum materials [117,118]. The left picture with many cracks represents the growth under the original "flat" temperature profile along the growth direction, whereas the right one with little cracks represents the growth under the improved "bell-shaped" temperature profile.…”