Systematics of EPR spectra of GD3+ in some isostructural rare-earth trisulphate octahydrate hosts

X-band data on Gd³⁺ ions doping some isostructural single crystals of rare-earth trisulphate octahydrate [R₂(SO₄)₃·8H₂O] single crystals (RSH) have been obtained at room temperature for the hosts characterized by R = Pr, Nd, Sm, Eu, Yb and Y, and at liquid nitrogen and liquid helium temperatures for the hosts characterized by R = Pr, Sm, Eu and Y. The data are analyzed using a rigorous least-squares fitting procedure in which all resonant line positions obtained for various orientations of the external magnetic field are fitted simultaneously to the same spin Hamiltonian parameters. The intensities of the lines obtained at liquid helium temperatures indicate the absolute sign of the parameter b₂⁰ to be negative for R = Pr, Eu and Y, whereas for the Sm host the sign of b₂⁰ is found to be positive. While the parameter b₂⁰ does not exhibit a clear cut linear dependence upon the host ion radius, the parameter b₂⁰ is found to behave approximately linearly as a function of the host-ion radius. On the other hand, the zero-field splitting is found to be a linear function of the host ion radius at all three temperatures—room, liquid nitrogen and liquid helium.A comparison is presented of the systematics of the EPR spectra for the RSH hosts with those for some other isostructural rare-earth hosts.