ELECTRON-PARAMAGNETIC-RESONANCE STUDIES OF GD3+ IN K2ZN(SO4)(2)6H(2)O

A single crystal of K2Zn(SO4)(2)6H(2)O doped with Gd3+ was studied by EPR at room temperature and at - 150 degrees C using an X-band spectro meter. There are two magnetically equivalent spectra characterized by the main Stevens constants b(2)(0) = 0.029 cm(-1) and b(2)(2) = 0.0217 cm(-1). The spectra are described by a general spin Hamiltonian and a ll constants have been determined. The zero-field splitting of the ene rgy levels is of the order of 0.3 cm(-1) and EPR lines exist at very l ow fields, which are identified. The spectra are temperature dependent . This is interpreted as an anisotropic modification of the Gd3+ envir onment. The analysis of the pseudo-symmetry of the fourth order term o f the spin Hamiltonian shows a strong modification of the local struct ure. The coordination polyhedra, of Gd3+ are different from Zn and K p olyhedra The comparison with other results from the double sulphate fa mily is made.