Sharp Structural and Magnetic Phase Transitions in High-Entropy Oxide (Mg0.2Mn0.2Co0.2Ni0.2Zn0.2)VO3.

Phase transitions in solid solutions generally tend to be broadened and diffused, often accompanied by the emergence of disordered phases. In this study, we report a contrasting result in a novel high-entropy compound, ilmenite-type (Mg0.2Mn0.2Co0.2Ni0.2Zn0.2)VO3, which exhibits a sharp structural phase transition accompanied by V-V dimerization, as well as an antiferromagnetic transition. (Mg0.2Mn0.2Co0.2Ni0.2Zn0.2)VO3 was obtained through high-pressure synthesis at 8 GPa and 1373 K for 1 h. At room temperature, the compound exhibited a triclinic ilmenite-type structure associated with V-V dimerization. Synchrotron X-ray diffraction (SXRD) and differential scanning calorimetry (DSC) measurements revealed that this compound underwent a structural transition to a rhombohedral phase at 510 K, concomitant with the disappearance of the V-V dimer structure. Furthermore, an antiferromagnetic transition was observed at 80 K through magnetic susceptibility and heat capacity measurements. The emergence of sharp structural and magnetic phase transitions, despite the high-entropy composition, represents a particularly noteworthy finding of this study.