Gd3+-Gd3+ Interactions in Rare-Earth Hydroxides

Abstract
Using the method of paramagnetic resonance of isolated ion pairs, we have measured the isotropic exchange interactions between nearest and next‐nearest Gd3+ neighbors in Y(OH)3 at 77°K. Defining Hex = Jij S i ·S j , we find Jnn = 1134×10−4 cm−1 and Jnnn = −60×10−4 cm−1. Comparable anisotropic interactions are closely accounted for by magnetic dipole coupling. Similar experiments on Gd3+ in isomorphic Eu(OH)3 give Jnn = 1035×10−4 cm−1. Taken together, these results allow a comparison with the interactions in pure Gd(OH)3, obtained from an analysis of susceptibility and specific heat measurements. General agreement is found. On the other hand, comparison of the present results with earlier exchange parameters of Gd3+ in isostructural La‐, Eu‐, and GdCl3 shows a striking trend for which there is no theoretical explanation.