Pressure-induced electronic and magnetic phase transitions in a Mott insulator: Ti-doped C a3 R u2 O7 bilayer ruthenate

We report the hydrostatic pressure-induced electronic and magnetic phase transitions in a Mott insulator, a bilayer ruthenate Ca3(Ru0.97Ti0.03)2O7, via electronic transport and single crystal neutron diffraction measurements. The system undergoes an insulator-metal transition at a very small hydrostatic pressure ≈0.04 GPa, followed by a magnetic phase transition around 0.3 GPa, suggesting that the low energy charge fluctuation and magnetic ordering couple to the pressure separately in this compound. The ab initio calculations show that the suppressed RuO6 flattening induced by the pressure reduces the orbital polarization and gives rise to an insulator-metal transition preceding the magnetic phase transition.