The observation of the insulator-metal transition in EuNiO3 under high pressure

The charge transfer antiferromagnetic (TN = 220 K) insulator EuNiO3 undergoes, at ambient pressure, a temperature-induced metal-insulator (MI) transition at TMI = 463 K. We have investigated the effect of pressure (up to p ∼ 20 GPa) on the electronic, magnetic and structural properties of EuNiO3 using electrical resistance measurements, 151Eu nuclear resonance scattering of synchrotron radiation and x-ray diffraction, respectively. With increasing pressure we find at pc = 5.8 GPa a transition from the insulating state to a metallic state, while the orthorhombic structure remains unchanged up to 20 GPa. The results are explained in terms of a gradual increase of the electronic bandwidth with increasing pressure, which results in a closing of the charge transfer gap. It is further shown that the pressure-induced metallic state exhibits magnetic order with a lower value of TN (TN ∼ 120 K at 9.4 GPa) which disappears between 9.4 and 14.4 GPa