Low-temperature anomalies in the magnetic and thermal properties of molecular cryocrystals doped with oxygen impurity

Abstract

The magnetic properties of oxygen pair clusters are investigated theoretically for different cluster geometries which can be realized by doping molecular cryomatrices with oxygen. Anomalous temperature and pressure behavior of the magnetic susceptibility, heat capacity, and entropy is predicted. It is proposed to use these anomalies for studying the parameters characterizing the oxygen clusters and the parameters of the host matrix: the effective spin-figure interaction constant D for the molecule in the matrix, the exchange parameter J, and the number of pair clusters Np, which can deviate markedly from the purely random value Np=6Nc2 (N is Avogadro’s number, and c is the molar concentration of the impurity). The data on the magnetic susceptibility may be used to analyze the character of the positional and orientational short-range order in the solid solution. The value of D contains information about the orientational order parameter; the distance and angular dependence of the exchange interaction parameter are still subject to discussion in the literature. The temperature dependence of Np contains information about diffusion and clusterization processes in the system.

Raman Investigation of the N2−O2 Binary System as a Function of Pressure and Temperature

“…Pritula and Khashchina 16 performed FTIR studies on the nitrogen−oxygen binary mixed system in the far IR and measured the O 2 -magnon frequency as a function of the N 2 concentration. Freiman et al presented theoretical studies of magnetic properties of oxygen pair clusters for different geometries that can be realized in the N 2 −O 2 binary mixed system. These authors predicted anomalous temperature and pressure behavior of the magnetic susceptibility, heat capacity, and entropy.…”