Magnetic Properties of FexO as Related to the Defect Structure

Abstract

The magnetic properties of FexO with long-range order of defects was studied. The crystal structure appears to consist of periodically spaced complexes of vacant octahedral and occupied tetrahedral sites, with most of the octahedral ions in an ideal NaCl-type environment. The Néel temperature, determined from measurements of susceptibility and modulus, increases very slightly as x is decreased. Octahedral-tetrahedral ion exchange interactions are proposed to account for the increase in TN. The molar susceptibility obeys a Curie-Weiss law, χ = 3.56/(T+136). With θ = 136°K and TN about 200°K, θ/TN is less than one. According to a treatment by Van Vleck one expects θ/TN greater than one for negative first-near-neighbor and second-near-neighbor interactions. A positive first-near-neighbor interaction may possibly arise through double exchange between Fe2+ and Fe3+.

The influence of oxidation process on exchange bias in egg-shaped FeO/Fe3O4 core/shell nanoparticles

“…M(T) shows the antiferromagnetic-to-paramagnetic transition of wustite at 205 K (in the as-made sample). According to [28,29] this value of T N can be assigned to non- Hysteresis loops were recorded after zero field cooling (ZFC) and 5 kOe field cooling (FC).…”

Wüstite: electric, thermodynamic and optical properties of FeO

“…The magnetic susceptibility of wüstite has been investigated by Bizette and Tsai [4], Ariya and Grossman [38], Koch and Fine [39] and by Srinivasan and Seehra [40]. The latter investigated the magnetic susceptibility just around the magnetic ordering transition, concluding that it is of first order.…”

Wüstite (Fe1‐x O): A review of its defect structure and physical properties

“…Transmission electron microscopy of wiistite on a heating stage could be used to elucidate T-T-T behavior of Fe•structural properties of wiistite are dependent on both composition (x) and structural state, which are in turn dependent on thermal and pressure history. Perhaps the most obvious examples of this dependence are magnetic properties[Koch and Fine, 1967;Greenwood, 1973; Battle and Cheetharn, 1979], which are particularly sensitive to the topology and distribution of defect clusters. Exsolved ferromagnetic phases such as metallic iron or magnetite may have an even greater effect on the observed magnetic behavior of wiistite.…”