Pressure-induced metallization and the collapse of the magnetic state in the antiferromagnetic insulator NiI2

The first observation of a pressure-induced metallization accompanied by the spontaneous collapse of magnetic ordering is reported. This isostructural concurrence is observed in the layered antiferromagnetic insulator NiI2. Electrical transport, x-ray diffraction, and I129 Mössbauer studies were carried out in diamond-anvil cells. The evidence points to a mechanism by which the originally filled 5p-iodide band shifts and overlaps with the partially filled nickel-3d states. The formation of a hybridized conduction band at P>19 GPa results in the onset of a diamagnetic metallic ground state.