Prokhorov A. EPR of transition ions in crystals with perchlorate hexahydrate structure: ef-fects of temperature and pressure.

The thesis is devoted to investigation of EPR spectra of 3d-metals Mn, Ni, Co in isostructural crystals [M2+(AB4)2*6H2O, M2+- Zn, Mg, Cd; A-B,Cl; B-F,O] as well as EPR spectra of rare earth Er3+ in KY(WO4)2 under high pressure and in a wide temperature region. EPR spectra of impurity centers in isomorphic fluorine-borates and perchlorates have been searched. Spectra of Mn2+ in Cd(BF4)2*6H2O and Co2+ in Zn(BF4)2*6H2O were observed for the first time. As a result of spectra and spin-hamiltonian parameters analysis it was established that the distortion of paramagnetic ion's ligand environment in fluorine-borates is different from the one in perchlorates. Mn2+*6H2O complex in fluorine-borates is stretched along c axis of the crystal (b20<0), whereas in perchlorates it is compressed along the same axis (b20>0). g-factor temperature dependence for 3d-ions (Co2+) has been discovered in low temperature region. The effect was con-firmed with the observation on Er3+. It was established that high-temperature phase transitions in perchlorates shift to higher temperatures and low-temperature ones shift to lower temperatures while pressure increases. It is assumed that low-temperature phase disappears under high pressure and this state exists in a closed area on phase diagram. Hydrostatic pressure expands temperature region of the phase and the crys-tals strive for uniphase state. Spasmodic transition T1 in Cd(ClO4)2*6H2O becames smooth under high pressure.