Electron paramagnetic resonance in RbH3(SeO3)2:Cr3+ crystals

Coordination and spin Hamiltonian parameters have been examined for two types of paramagnetic Cr3+ centres in RbH3(SeO3)2 monocrystal. On the basis of temperature analysis of the EPR spectrum in the range (77-300)K a different type of coupling between the complexes 1 and 2 and the lattice has been found. Due to the new method EMM EPR was possible to examine the superstructure occurring below the Tsub(c) as a result of the symmetry change P212121 to P21 and to define the relation between the splitting of the EPR spectrum and the domain structure. The eta order parameter determined from EPR measurement corresponds to the rotation of the SeO3 groups in the ferroelectric phase. (author)