Magnetic properties of solid oxygen under pressure (Review Article)

Abstract

Solid oxygen is a unique crystal combining properties of a simple molecular solid and a magnet. Unlike ordinary magnets, the exchange interaction in solid oxygen acts on a background of weak Van der Waals forces, providing a significant part of the total lattice energy. Therefore, the magnetic and lattice properties of solid oxygen are very closely related. This manifests itself in a very rich phase diagram and numerous anomalies of thermal, magnetic and optical properties. Low-temperature low-pressure α-O2 is a two-sublattice collinear Neel antiferromagnet. At a pressure of ∼6 GPa, α-O2 is transformed into δ-O2, in which three different magnetic structures are realized upon increasing temperature. At ∼8 GPa δ-O2 is transformed into ε-O2. In this transition, O2 molecules combine into four-molecule clusters (O2)4. This transformation is accompanied by a magnetic collapse. This review describes the evolution of the magnetic structure with increasing pressure, and analyzes the causes behind this behavior.

Magnetism in Solid Oxygen Studied by High-Pressure Neutron Diffraction

“…More recently, the properties of solid oxygen -including its magnetic propertieswere reviewed in a very detailed and highly useful article by Freiman and Jodl [11]. There is also a more recent review by Freiman [12] with a focus on magnetism in solid O2. To avoid unnecessary overlap with this and previous work, I will present here a detailed review of high pressure neutron scattering results published from 2004 on, obtained with techniques which allowed the investigation of the five phases of solid oxygen which exist in the 10 GPa range, i.e.…”