EPR of impurity ions in disordered solids

The state of the art in the EPR spectroscopy of disordered solids is reviewed and theoretical aspects of the EPR shape in disordered systems are discussed. Emphasis is placed on the concept of the joint probability density of the spin Hamiltonian parameters. A survey of experimental data is provided on distributions of spin Hamiltonian parametes obtained using computer simulation techniques. A quantitative information is given on the short-range ordering in disordered materials available from EPR studies. A procedure of extracting such type of data which consists in a transformation from the distribution of the spin Hamiltonian parameters to that of atomic coordinates in the surrounding of a paramagnetic center is outlined. Numerical estimates of the degree of continuous disorder are reviewed