Antiferromagnetic Metallic Phase Research Articles

Conductivity transitions in itinerant-electron systems: Experimental evidence for an antiferromagnetic metallic phase

Approximate solutions of the simplest model of correlated electrons in a narrow band predicts the appearance of an antiferromagnetic metallic phase after the Mott transition as Δ/U is increased at T = 0. It lies between the antiferromagnetic insulator and the non-magnetic metal. This phase is absent from the observed electronic phase diagram of V2O3. NiS, however, is a semimetallic antiferromagnet below its first order conductivity transition and its properties, particularly those requiring an itinerant-electron model for the magnetism, are summarized. In the system (Fe1−xNix)S, itinerant and localized moments coexist, and an antiferromagnetic insulating phase is not obtained. The recently-reported electronic phase diagrams of solid solutions of NiS2 (an antiferromagnetic semiconsuctor) and NiSe2 or NiAs2 (non-magnetic metals) show a region where the systems are antiferromagnetic metals. Among the transition metal compounds these systems may be the ones which best correspond to the Mott-Hubbard model.

PHYSICAL PROPERTIES OF COMPOUNDS NiS2-xSex WITH PYRITE STRUCTURE : METAL-NON METAL TRANSITION, EVIDENCE FOR THE EXISTENCE OF AN ANTIFERROMAGNETIC METALLIC PHASE

We discuss the physical properties of mixed compounds NiS2-xSex. In this system for x ~ 0.45 an insulator-metal transition occurs which is interpreted in the sense of the model of Mott and Hubbard. Our experimental results (susceptibility, N.M.R. with 77Se, Mossbauer spectroscopy with 61Ni and neutron diffraction) demonstrate the existence of an antiferromagnetic metallic phase (AFM) in the range of concentrations 0.45 ⩽ x ⩽ 1. The magnetic properties of the AFM phase are discussed in terms of a model which implies a strong influence of the local environment on the magnetic state of nickel atoms.

Existence of an antiferromagnetic metallic phase (AFM) in the NiS 2−xSe x system with pyrite structure

The study of the physical properties of the system NiS 2− x Se x shows the existence, in the range 0.6 ⩽ x ⩽ 0.9, of an antiferromagnetic metallic phase (A.F.M.) as predicted by the Mott-Hubbard theory and which has not been previously observed in such systems.