Structurally-driven metal-insulator transition in Ca₂Ru _1-xCr_xO₄ (0≤x<0.14): A single crystal X-ray diffraction study

Correlation between structure and transport properties are investigated in high-quality single-crystals of Ca₂Ru_1-xCr _xO₄ with 0<x<0.14 using single crystal X-ray diffraction and by electronic studies. The parent compound was known to exhibit an intriguing first-order structurally driven metalinsulator (MI) transition at 357 K. Upon chromium doping on the ruthenium site, the metalinsulator transition temperature (T_MI) was drastically reduced, and is related to the competition between structural changes that occur upon Cr doping and with decreasing temperature. A strong suppression of structural distortions with increasing Cr substitution was identified. No clear T_MI can be observed when x>13.5% and the system behaves as an insulator. Such a large, sharp metalinsulator transition and tuneable transition temperature may have potential applications in electronic devices.