EPR OF GD3-SYMMETRY( IN SULFATE HOST CRYSTALS OF LOW)

Electron paramagnetic resonance (EPR) spectra of trivalent gadolinium have been investigated in orthorhombic sulfate host crystals MeSO4 wit h Me=Sr, Ba, Cd, Hg, Pb and K2SO4. Because of the low symmetry of the host crystals and the spin quantum number 7/2, complex spectra for sev eral orientations of the magnetic field containing a large number of i ndividual lines had to be analyzed. The spin Hamiltonian parameters ha ve been rigorously determined from the rotational diagrams. Gd3+ has b een found to substitute, first of all, for the monoclinic sites of the host metal ion with charge compensation at larger distances. To a sma ll extent, charge compensation in the vicinity has also been observed, arising from additional centres and spectra with lower intensities. C orrelations between EPR spectra and crystal structure are reflected in the values of the zero field splitting parameters.