Pressure-induced metallization and the collapse of the magnetic state in the antiferromagnetic insulatorNiI2

Abstract

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 Nih. Electrical transport, x-ray-diffraction, and ,29 I Mossbauer 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.

Pressure-Induced Metallization and Electronic-Magnetic Properties of Some Mott Insulators

“…This strongly suggests that there is no volume change and that the transition is second-order. The smooth behavior of V(P) was also established from XRD studies [4]. Similar findings were observed in the analogous FeI 2 (d 6 ) and CoI 2 (d 7 ).…”

“…In Fig. 1b we show the similar dependences in Ni 129 I of the IS, H hf , and T N on the normalized volume decrease DV/V 0 , the latter deduced from equation of state data [4]. Note that up to 19 GPa, the critical pressure P c at which the Mott transition occurs, both the isomer shift (IS) and T N scale linearly with volume.…”

“…The first unambiguous observation of a pressure-induced Mott transition was in NiI 2 (Pasternak et al [4]) employing 129 I MS, XRD, and resistivity methods. Following this study, measurements were also carried out in CoI 2 , FeI 2 ( 129 I and 57 Fe MS probes) and recently in FeCl 2 [6].…”

“…A typical Mott transition will involve a concurrent IM transition and the loss of ionic magnetic moment. Pasternak et al [4] reported the first unambiguous observation of a pressure-induced correlation breakdown in NiI 2 using DACs and a combination of measurement techniques.…”

The Mott insulators at extreme conditions; structural consequences of pressure-induced electronic transitions

“…A notable example pertinent to the nature of these strongly correlated systems has been the discovery of the pressure-induced Mott-transition in NiI 2 [15,16]. No detectable structural changes at the transition range have been observed.…”