Christov A. High spin - low spin phase transitions in Fe2+ ions coordination compounds under pressure

The experimental and theoretical study of hydrostatic pressure influence on temperature induced spin transitions in the iron(II) spin crossover complexes, which are located in metalloorganic compounds, is considered in the dissertation. Research methods are X-ray diffractometry, differential scanning calorimetry, magnetometry. It was established that the spin transition characteristics depend on linkage type between complex molecules and complex mechanism of elastic stress redistribution between molecules and lattice. The lattice elastic energy and interaction energy contributions can be divided in the cooperative spin transition. The elastic energy controls a transition temperature and the complexes interaction controls a hysteresis width. The spin transition microscopic model under pressure is offered. It not only describes this phenomenon on the whole but also allows to reproduce the experimental behavior of spin transition in the real metalloorganic compounds. The quantitative connection between the microscopic model and phenomenological model in mean field approach has been found.