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

Low-Temperature Physics and Chemistry in Cryomatrice

Анотація

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 N_p , which can deviate markedly from the purely random value N = 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 is still a subject of discussion in the literature. The tempearture dependence of N_p contains information about diffusion and clusterization processes in the system.