  The magnetization process of the breathing pyrochlore magnet CuInCr4S8 has
been investigated in ultra-high magnetic fields up to 150 T. Successive phase
transitions characterized with a substantially wide 1/2-plateau from 55 T to
110 T are observed in this system, resembling those reported in chromium spinel
oxides. In addition to the 1/2-plateau phase, the magnetization is found to
exhibit two inherent behaviors: a slight change in the slope of the M-H curve
at ~ 85 T and a shoulder-like shape at ~ 130 T prior to the saturation. Both of
them are accompanied by a hysteresis, suggesting first-order transitions. The
theoretical calculation applicable to CuInCr4S8 is also shown, based on the
microscopic model with the spin-lattice coupling. The calculation fairly well
reproduces the main features of the experimentally observed magnetization
process, including a relatively wide cant 2:1:1 phase clearly observed in the
previous work [Y. Okamoto et al., J. Phys. Soc. Jpn. 87, 034709 (2018)]. The
robust 1/2-plateau on CuInCr4S8 seems to be originated from the dominant
antiferromagnetic interactions and the strong spin-lattice coupling.
