ESR Investigations of Nearest-NeighborGd3+Pairs in Lanthanum Ethyl Sulfate

Abstract
The ESR spectrum of nearest-neighbor Gd3+ ion pairs in single crystals of hydrated lanthanum ethyl sulfate containing approximately 0.1- and 1-wt.% gadolinium has been identified and measured at 77°K. It has been found that the nature of the pair interaction is primarily dipolar, although a small superexchange interaction is also present. The best theoretical fit of the experimental pair spectrum is obtained with a spin Hamiltonian characterized by the crystalline-field parameters b20=188, b40=3.2, b60=0.4 and the dipolar and exchange interaction constants d=45 and J=2, all in units of 104 cm1.