Low Temperature Physics: 26, 767 (2000); https://doi.org/10.1063/1.1312406 (11 pages)
Физика Низких Температур: Том 26, Выпуск 9-10 (Сентябрь 2000), c. 1029-1043    ( к оглавлению , назад )

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

Yu. A. Freiman and S. M. Tretyak

B. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine 47 Lenin Ave., 61164 Kharkov, Ukraine
E-mail: freiman@ilt.kharkov.ua

A. Jeżowski

Trzebyatowski Institute for Low Temperatures and Structure Research, Polish Academy of Sciences, P.O.Box 937, 50-950 Wroclaw 2, Poland
E-mail: an_je@int.pan.wroc.pl

Received May 17, 2000


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 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 Np contains information about diffusion and clusterization processes in the system.

36.40.Cg - Electronic and magnetic properties of clusters
65.40.+g -
65.40.+m -
75.40.Cx - Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)